how can i tell if my sister is mentally ill. About 15 years ago she started hating people without cause. She is a loner she lives with her brother and sister yet she doesn t speak to them unless it is necessary. she doesn t have a single friend. When relatives come to their house for a visit she gets angry. She says words of insult to them people stop visiting my brother and my other sister who lives there. I am her sister she hates me no reason I don t even live in the same state as her. When My sons got married 3 yrs ago she started to get angry. she is an old maid . What must I do? the whole family is in a mess because of her behavior. She stopped talking with my two sisters in-law. She has a job . Her personality has totally changed. She cooks for herself and hide the food, she used to cook and share it with her family. I real don t know what to do? She became very jealous of me for getting married and having my children. Is there anyway I can help her? Please help me help us. Thank you, Marta