Wait, so she’s not even related? It sounds like MC stopped facing reality years ago, then. Hell, I can’t figure out what you refer to her as an in-law at all.
I’m really, really sorry to hear this because it sounds like your relationship is headed, rapidly, for a brick wall. I could not stand having my SO’s brother and his kids mooching off us, forget someone he thought was his soul brother. And I have hastened to assure him many times that my dimwit useless half brothers will never be staying with me.
However, youll never win with the “masters in special education” gambit. This is the kind of game where the only way to win is to not play at all - that is, default, and maybe get counseling, and quite possibly move out.
I’m really sorry because it doesn’t sound like your relationship is a bad one other than this mess. 
That point sticks out to me, too - someone on these boards said at one time, you can’t use logic to argue someone out of a position that they didn’t use logic to get into in the first place.
I only used the Master’s Gambit in this last one simply because I’m tired of the accusation “You have a master’s and you keep ignoring that she has a disability.” Yeah I have a MA in SpEd so maybe you should trust me that I know what I’m doing/saying. Like I said that did not go well.
Sorry you are going through this, i can just feel the frustration and resentment coming through your posts. I don’t think your wife is going to face reality unless you force it on her.
You must have a lot more patience than I do; I think at some point my response would be, “SHE DOESN’T HAVE A FUCKING DISABILITY! SHE’S A FUCKING LEECH WHO NEEDS TO GET A BETTER FUCKING JOB AND LOOK AFTER HER FUCKING CHILD LIKE AN ADULT!”
That wouldn’t win any arguments. 
Oh, I wasn’t blaming you. I know the temptation! But it’s clear that’s going to just come off as you being a know-it-all. She has her fingers firmly in her ears.
I really, really sympathize with you. What a stupid reason for a marriage to potentially come to an end. You simply can’t have someone else living in your house for 2.5 years, mooching, without a great deal of stress.
Why don’t you give the dad a call? Tell him you don’t think his daughter is being raised in a suitable environment. Maybe give him the number of a local law firm.
It’s time to have an adult conversation with your wife. Be open, be honest. You’ve tried, very hard, yet find you cannot go on like this. Tell her you will not be moving with her and SIL. Refuse to argue or fight about it any more. Hard truth time: you cannot do this any more, the frustration is killing you.
Set about finding a place for yourself alone, wherever you were moving to. Then move to it. Let the sisters work it out between them. Stand back and wait and see what shakes out.
Much cheaper than a divorce lawyer, and wakes everybody up, or not, from their denial. See if that doesn’t change things for each of you. Sounds like you could all use some time apart. If this is your line in the sand, then prepare to make a stand.
But first accept that this may be the end of your marriage, you won’t be able to pull any of this off until you can do so without engaging in trying to change her mind or going over it one more time. When you can get to THAT place, you’re probably ready to move forward with as little drama and acrimony as possible.
I wish you good luck with it all and appreciate the depth of your frustration!
I agree with this. You cannot force your wife to change. You cannot force her friend to change. All you change is your own enabling of this friend’s behavior.
I don’t blame you for being angry, but I think it is a good idea to try to avoid letting he conversation about this be an angry one. Just simply state the facts that you feel this is too much for you and you cannot be part of it anymore.
I think this is unfair. I have two sack of shit brothers (neither works, both do drugs, and are master manipulators of my crazy, enabling mother) with seven kids between them. The oldest brother lost two of his children so they have custody of two and three respectively.
I would NEVER let them stay with me and every time they wind up at my parents’ house, I actively encourage them to kick the brother and his kids out. My parents have been married for more than 35 years and have never been even close to divorce except when one of my brothers, or any combination of their children, lives with them. Their health suffers from the added stress in their house and their marriage. But my mom insists on doing it “for the grandbabies.” I think she’s nuts. And it isn’t because I don’t care about my brothers or their children, it’s because I think there’s only so much you can do for somebody before it stops being helpful and becomes unhealthy and because I firmly believe that my parents (and myself and the OP’s wife) have a greater responsibility to themselves and each other than to grown people who refuse to get their shit together. That those grown people have offspring is largely irrelevant, in my opinion.
In other words, if you have the bad luck to be born to loser parents, sucks to be you. Nice.
I’m going to ask you to turn off the immediate moral outrage and consider this wacky plan:
Turn the niece against the SIL.
Start spoiling the kid rotten, treat her as if she’s your own. You already have a unique situation with the wife and the not-so-sister-in-law, so I believe this will be easy for you. Every time that SIL neglects the kid or makes her upset, whether its justified or not, swoop in like a knight in shining armor. Get her that toy the mom can’t afford, take her to the places that the mom is too lazy to take her, treat her like how she wants to be treated (whether like a little adult, a little baby, a transgendered boy, a my little pony, etc.) and tell her she’s right all the time, especially if you know it goes against what SIL wants.
After a little while of this, start blaming everything on SIL, even stuff that isn’t her fault and especially if she can’t change it. Once the niece trusts you, start withholding your gifts and your affections, blame it on SIL. Can’t afford that new Barbie Dream House? Point out SIL has new shoes or a new purse and that’s why. Can’t take her out to the zoo or something? Tell her SIL needed your attention for something else.
The purpose of this is to create a foundation in order to isolate SIL from the rest of the family. Assuming your wife thinks of the niece as a surrogate daughter, her youth and vulnerability should engender sympathies that wouldn’t necessarily be duplicated with the SIL. Eventually, if forced to choose, you can make the very logical argument that SIL’s situation is her own fault and you have to take care of the niece first because she’s a child. That should bring both niece and wife on your side against SIL, making it easier to push her out. After that, just drop off the kid at BIL’s house and you’re done
I’m not exactly advocating that. Its evil and you shouldn’t do it. But your situation’s desperate and desperate times calls for desperate measures. I have no idea how I would react if I had 2 strangers living in my house sucking off my wallet, forcing me to take another job and have no end in sight. I may flip out and kill everyone. So before that happens to you, consider this plan. Its devious, but it may work. Console yourself thus: the kid will get over you, she’s young, and the success of this plan results in her reuniting with the more responsible parent. It creates a healthy distance between your wife and a moocher of a childhood friend. The one most hurt is the SIL, who deserves it, so tough shit. And you get your house and family back
I don’t think that’s what she’s saying; I think she’s saying that crappy parents like this use their kids as their excuse to freeload rather than look after their kids properly themselves.
I think it hurts the eight year old, too - first she gets everything she wants, then she doesn’t get anything, then she’s turned against her mother - I think it would mess her up too much.
Seriously, though - the girl has a father who, unlike her mother, is capable of putting a roof over her head. Shouldn’t she be living with him?
+1. Unless there’s something we don’t know about the father, he’s apparently the more responsible parent and will provide the best home for the child.
Yeah, it’s been mentioned before, I think, but thinking more about it, has the father been involved in these discussions at all? Can you go to him, Saint Cad, and tell him that he needs to take his daughter in before his ex-wife ruins your marriage?
So how do you solve this? I agree that enabling does no good, but I don’t think writing off the whole clan is terribly helpful either. I’d strive for the middle ground: build a good relationship with the kids, model functional adulthood, and minimize contact with the adults.
That’s what makes dealing with moochers with kids so difficult - sure, you can kick an adult out and expect them to sink or swim on their own, but who can kick little kids out? The mooching parents know this and play on it.
Thank you, that’s exactly my point. My brothers have used “The baby needs diapers/formula” more times than I can count to get money from my parents. I would bet every dollar they’ve taken from my parents (and it must be a ridiculous, astronomical amount) that the vast majority went to them and their wants, needs, drugs, etc. NOT their children. They know that nobody will say, “Too bad, let them starve,” but my parents likely would not give them money because they need gas to get dope, or whatever. They bank on the fact that “oh no, think of the children!” will defeat the better judgment of smart people. And they’re right.
My brother asked me for diaper money once, years ago. I told him no but offered to bring diapers. He got pissed, declined, and said he’d “figure it out.”
It’s unfortunate that there are parents who don’t care enough about their children to do right by them. But should people really be expected to sacrifice their money, time, effort, sanity, spousal relationships, the happiness of their own children*, etc past the point when it could possibly be considered “helpful”? There is a world of difference between somebody staying with you for two weeks while they find a place and moving in with no plan at all. After 2.5 years it must be clear that you’re throwing away your resources and for what?
*My sister let my brother and his two remaining children stay with her family for some time. Every single one of her children (five, and there wasn’t even close to enough space for everybody) were completely miserable. So was she. So was her husband. And she bitched all the time to me about it, I’d roll my eyes and tell her to get rid of them. She “couldn’t.” Her whole family was miserable, her own children, and somehow caring about the well-being of a grown man and children he chose to have became more important. That’s completely insane to me. That this thread even suggests the end of a marriage because the needs of a third party somehow trump the needs of the marriage is completely insane to me.