OK, cheating isn’t an issue. Very open-minded of you.
Because her behavior is making you feel bad, and he’s not helping. You at least deserve an explanation from them.
Laurange,
IMHO,
She is threatened by the fact that you are the first serious contender for his heart since the two of them split up. She is possibly jealous of you and dosent want to be around you because she might still want to be around him, and it hurts exes to se their old S.O.'s with someone else.
She feels threatened by you because your SO is in a committed relationship with you, and not her anymore. I’ll be willing to bet that he stopped the “comfort sex” they were having. she may have thought that there was a chance they would get back together, and when he stopped sleeping with her she realised that you meant more to him than the other women.
Really push to meet her, and create a good impression. Show her that you don’t mind her being friends with him, and that you aren’t the Ogre she may think you to be.
[springer]
Until then, take care of yourself, and each other
[/springer]
I could offer a whole different point of view regarding the nature of the female species when it comes to ex’s and extremely irrational behavior, but as a wise man once said, “Some things are better left unspoken.”
BH
Yes, Black Hole, espeically since it isn’t nice to hijack other people’s threads and we’d both get banned in the process. 
I think Billdo and wyldelf hit it right on the head. The ex is being manipulative and selfish, and your BF needs to understand that. If it makes him uncomfortable to see her (“Ugh, I have to go see blank tonight.”), then that should tell him something. She’s not going to get over him as long as they’re still spending so much time together, especially since she goes to such great lengths to avoid acknowledging that he has moved on.
I agree with Geobabe in saying that Billdo and wyldelf are right. The next time he says, “Ugh! I have to go see [blank] tonight,” just tell him - “You don’t have to do anything you don’t want to do.” Then maybe you can help him see that he’s not doing his ex any good by being around her right now. She needs to accept his new relationship and move on with her life but she can’t do that as long as he is spending so much time with her.
I think I just repeated what Geobabe said. I should’ve just said Ditto!
I see that you trust your boyfriend explicitly, but do you trust her?
No matter HOW much I trust my husband, I would NEVER stand for him being alone with another woman who was in love with him. Call it pissing on trees, call it whatever you want but I will guarantee that her motives are not pure.
Tell your SO that you find her actions rude and her repeated refusals to be friendly are downright demeaning. Tell him to invite her over (or meet for dinner) and insist upon it.
This woman has got to understand that she has no chance with him. Him continuing to meet her, on her terms and without you, is sending the wrong message. Whether you like it or not, she’s got the control in this triangle and you need to get it back.
Lay down the law. This isn’t about trust, it’s about respect. She’s not respecting your relationship and your SO isn’t being very respectful of it either.
JMHO, YMMV
As a woman who has traditionally remained very close with almost all exes, I understand where you’re coming from as well as the other side of the issue.
Mostly, I wanted to expand on wydelf’s statement.
You have already said that for other reasons, this person doesn’t like you. If I could tell you the enormous amount of energy I have spent successfully “running off” new girlfriends because I didn’t like them, or did like them but didn’t think they were right for my friend, or thought were just stupid or annoying, etc… in the name of “friendship” you might be significantly more worried about the fact that she isn’t acting like “your” friend, but his alone.
If your relationship has a long-term future, this dynamic needs to change. If she supported your relationship, she’d be getting to know you better and trying to find common ground. If she doesn’t, and that’s what it sounds like, be certain that she’s probably working against it, passively if not actively. That’s what “friends” do when they think a loved one is a relationship they oughtn’t be. I think it’s safe to say, based on your posts, that whether or not it’s mutual, she considers him one of her loved ones.
If it is such a chore for your B/f to hang out with her on her terms, what is it that he is getting out of this that keeps things this way? You mentioned she was going to have a party and invite everyone in your circle but you? Ridiculous! Watch your back. Something like that is the social equivalent of declaring yourself as an enemy. That goes beyond “not friendly”, it’s deliberate exclusion. It’s a demonstration of animosity toward you and a display of territory towards him.
Maybe I’m being a little too political here, but LaurAnge, sweetie, watch your back.
I agree with just about everyone.
I went through a situation where I continued to maintain friendly contact with an ex (albeit at a distance; we were at separate universities) for years, and then made the mistake of inviting her to my wedding. Big mistake. It turned out she was still carrying a torch big enough to light Toronto. There was a scene. Things got ugly. Nuff said.
In the aftermath, a wise friend said the following to me, and I’ve kept it as a reminder:
I’ll leave it to you to decide how useful that is in your case…
jr8
What **Rachelle, Sue Duhnymh, Billdo, Geobabe and wyldelf ** said.
Ditto what most everybody else has been saying. In a nutshell:
The ex-gf wants him back. Not just as a friend, but as a relationship.
The bf (your current, her ex) wants to be a good guy, and maintain a friendly acquaintance with the ex-gf. This is certainly possible for healthy adults. For example, I’m very good friends with an ex-gf, as well as her husband, who happens to be the guy she dumped me for. Time and introspection allowed everyone to move on, and we’re all friends – including my current wife as well.
The ex-gf doesn’t just want him to be a good guy, she wants him back romantically. She has discovered, however, that she can play on his need to be a good guy, and manipulate him into sticking around, even in a limited capacity. She is biding her time, hoping that his current relationship with you sours, so she has a shot at getting him back.
Possible outcomes:
She finally gives up hope of re-establishing a romantic relationship, and allows herself to be recategorized as a friend. Or…
She finally gives up hope of re-establishing a romantic relationship, but doesn’t allow herself to be recategorized as “just” a friend, so she cuts off contact with the ex-bf herself. Or…
She never gives up hope of re-establishing a romantic relationship, and you and the bf stay together forever, so the whole uncomfortable situation is drawn out until the day somebody dies. Or…
She never gives up hope of re-establishing a romantic relationship, you and the bf break up (whether over this or something else is irrelevant), and she takes another shot. Or…
She never gives up hope of re-establishing a romantic relationship, and eventually starts actively trying to sour his relationship with you.
There are other possible outcomes, of course; you could all be burned to death in a freak waffle-iron accident. The possibilities above are more likely, though.
So in other words, the only alternatives that are positive for your relationship with the bf involve the ex no longer exerting her past-relationship influence on him. Period. He certainly thinks he’s doing the right thing, and (as far as I know) he should be commended for having good intentions. Unfortunately, you need more than good intentions to have a good result.
Essentially, he is allowing the uncomfortable situation to continue, because his behavior is “enabling” (modern psycho-speak buzzword, yeah, I know) the unhealthy person (the ex) to continue her behavior. He thinks he’s trying to help her, and again he gets some credit for intending to be a good person, but in reality, because of the conditions she has set for their “friendship” (primarily, the one that denies your existence), he’s permitting her to persist in the pursuit of her objective, which by definition runs counter to both yours and (as you describe it) his.
The bottom line is this: She is deliberately and actively trying to remove you, so she can get him back. This doesn’t really hurt you. What hurts you is his participation in her scheme. He may not really think that’s what he’s doing, but he is. (His saying “ugh” may be a subconscious confession of his awareness of this.) He needs to understand what he’s really doing, beyond what he thinks he’s trying to do. Once he does, once he knows that he’s essentially giving her permission to continue trying to break up your relationship with him, he can really do the right thing, as described by other posters above.
Just my two cents.