Perhaps this was the real reason for the drop by?
That would be my reaction, too
This. And there are still social groups in which it’s acceptable behavior.
But, even then – if you knocked on the door and nobody came, and knocked again and still nobody answered – you went away again. You didn’t keep on and on trying to beat the door down.
And if somebody did answer the door and said ‘sorry, this is a really bad time, please come back another day’ – you politely went away and came back another day; and didn’t accuse them of being rude. “Dropping by” really only works if “sorry, not right now” is considered acceptable. – Probable exception for people who had travelled two days to get there; but, by the time I was old enough to remember, people did call ahead, or at least write, if they were going to travel two days to get there.
I probably would have let them use the bathroom – and hoped that when they saw the state of the house they’d understand why nothing else was on offer.
And if they didn’t take one look at the place and get out of there after pissing, I would definitely have put them to work.
Whatever your social rules are: no, not everyone knows the same ones.
You could’ve pretended to be happy they stopped by and promptly put them all to work doing chores. 
Betcha that would make your niece hurry in a leave.
What if you hadn’t been home at all? How long would they have stood there on your front porch knocking?
If you are a socially aware adult. 
I visited my best friend’s house all the time. I’d bike over, or walk. We lived in the country. One day when I was about 12 I decided to go over without calling. No one home. The house is never locked (it isn’t right now, either) so I just went in and looked around. Couldn’t figure where everyone was. Eventually I left. I don’t think they ever knew how stupid I acted, thank goodness!
I mean, I get it. I personally don’t mind if people drop over (but nobody does anymore – it’s been nigh 20 years since I’ve had someone pop in 
). And I certainly don’t do it to anyway, as we’re all interconnected now with our phones. But not letting the kids use the bathroom is a level of cold I couldn’t stoop to. I’ve had near-strangers let me in their house to piss.
Someone knocks on my door might see the barrel of a gun answering.
No one has ever knocked. We knew who was coming and opened the doors when they drove up.
Can’t get to my door without my gate being unlocked by remote, after we get the alarm in the house.
A person walking up would have had to walk a long long way through the woods. I definitely don’t want to see them and they’re most likely up to no-good.
And that is what is wrong with America. Next step: preemptively shoot them, it’s the only way to be safe.
Ummm …never shot anyone yet.
You don’t live where I do.
I know this because I have no neighbors.
My meaning is, if you come up to my house, I know, you know and the whole family knows you’re not supposed to be there.
You will be met with suspicion, caution and an amount of fear.
Yes, I will protect myself and my family and property.
Can’t count on police, they are at least 30 minutes away.
If that’s an American problem it’s too bad.
If you make it MY problem by coming to my house unannounced, I’ll return the favor.
Yes, proper etiquette would be to call or text before a “pop in”. But I can’t help but think the OP is not presenting herself in a particularly flattering light. Which they probably don’t care about if their main overriding desire is to be left alone.
If this is a relative you are interested in maintaining a relationship with, it wouldn’t kill the OP to take a few minutes out of her busy day of cleaning for some cordial chit chat and let them use the bathroom.
Then again, if the goal is to be left alone, be as surly as you like.
Tell that to my in-laws!
You know what’s funny - I know a couple of people have acted similarly. And then later wondered why the same person who they wouldn’t let in to use the bathroom or who they wouldn’t chat with for a few minutes no longer calls/visits them.
If they’d accepted the first “This is not a good time for me to have guests,” sure. After ignoring and arguing her clear “no” repeatedly, fuck 'em. There’s no way that they would have “just” used the bathroom - once they’re in the front door, they aren’t leaving until they decide they’re done “visiting”.
I accept that is the more logical answer; just not my style.
Yeah, in fairness my personal style would be to let them in right away, then silently fume about it for ten years.
My sympathies are with the OP but the niece is going to tell the family that the OP was being rude.
By pointing a gun at a stranger, for daring to knock on your door?
OK.
Strangers not welcome in these here parts.
They will not be asking to pee.
They would be there for nefarious purposes only. Believe me.
(Others, read my whole post, not just the part they clipped out)
Hopefully the family will clue her in. “You did what???” “that’s not cool” “You should apologize.”
To get there they would have had to bypass a bunch of security and would be the equivalent of someone knocking on your bedroom door. Not to mention culturally appropriate to be met with a weapon. Probably a better move to text first.
When I was in college in the 80s, drop ins were completely acceptable in suburbia. We had friends who lived walking distance and sometimes people would happen to be in the area. It’s unheard of now. I don’t answer the door if I’m not expecting someone. I can see who it is on my doorbell camera now so if for some reason it is someone I know, I can choose to answer. When I am sitting on my couch in the living room, people can see me through the front window when they approach the house. They will see me look at them and then go back to my laptop posting here or on reddit.