You used "we"; who else is there and can they help you and/or help take care of her? Or, can you move out with friends for the time she'll be around? She doesn't have anyone in New York at all that can be called on to care for her up there?

She may bash you around but now you've seen her down and can just point that out (as you exit the room/wherever she is). I think she'll be feeling pretty poorly, might not be the same person she was as a child and you certainly don't have to respond the same; it's your territory now, she left.