She is not actually my sister in law. She is my boyfriend's brother's girlfriend. My boyfriend and I have been together for 5 years, and they have been together for 2.
She is constantly trying to compete with us to be the "better couple". When her boyfriend is not around she is saying ridiculous things such as planning to get pregnant, convincing him for a proposal, or even telling friends about the lies she tells him. This is in front of me!
She is constantly rude to me when we are in the presence of others, but when we are alone she tries to act like we are friends. She makes plans with her boyfriend and mine, and tries to make them when I am busy so I can't go. My boyfriend is also annoyed by her behavior but does not want to upset his brother. I don't know what to do about her constant annoying behavior, or how to approach my boyfriend's brother.
We had a problem last year and we all talked about it and "resolved" the problem - but I found out a month later that she was badmouthing me to the family members and even my friends! She is immature now to the point that she doesn't even say hello when coming over, and when I say hello to her, she will say hi as she is walking away or leaving the room. She has no respect! I don't know what to do about this but I am at the breaking point...
The most recent annoying behavior - she goes into my boyfriend's room, and will lay on his bed as if its her own. She writes things on his stuff that ends with hearts or x's and o's. This, to me, is inappropriate. I do not know if she is doing this because she is just immature, or trying to get under my skin. Advice please!