My boyfriends sister is very possessive, jealous and although he has tried to get her to include and respect me she ignores me and tries to seek him out alone. she is often rude and says inappropriate things. When i have responded back rudely to her, she seems to only see that I have offended her. What type or is there a type of disorder like this so I can understand it and deal with it better. My boyfriend is trying to set limits with her and she gets very upset.