I'm dealing with my 7 year old niece who is driving me insane. She hates my 8 year old son. My niece is living with me and I am the taking care of her pretty much all day because her mom is in school. She refuses to talk to my son at home. Pushes him and makes sure he doesn't get along with my older son who is 10. Luckily both my boys were raised together from day one and adore each other.  I'm due with another baby in two weeks and she constantly tells my son that it's her baby. She will forever take care of him and that she will make sure he never sits with him. My son started crying yesterday and I had to come in between the whole conversation. I don't know how to deal with her mean streak. I am only used to dealing with boys and she is driving me nuts. My boys never are mean to each other and this is the first time I have to deal with something like that. Every time I tell her mom about what happened she tells me to leave them both alone and let them sort their own problems. Is she right ?? Am I being sensitive??