What is wrong with my sister?

my sister is in her late twenties, she has never had a job. she is always very child like playing with cats and saying, "i love you mummy and daddy". she refuses to sign on the dole (unemployment money) even though it would help the family. she is not agoraphobic really since she can go out when she really needs something, but she stays in pretty much all the time.She has always hated me for not reason, always wanting to be with her mother, giving me dirty looks. so umm.. is there something odd/wrong about her?