Re: need to know whats wrong with her
I think your Aunt is putting too much pressure on the older one.I would suggest you give her a book "Family First" By Dr Phil McGraw, and ask her to read it for the sake of her family. Tell her that positive reinforcement with the kids work much better then the negative one.Also she should not hit her kids.
Also ask your mom to talk to the Aunt in a positive way and ask her if all the problems that are going on with her personal life, affecting the way she parents her kids or not..hopefully she will realize that and treat her kids much better.