Why is my stepmom a major ***?

Ok so my dads girlfriend lives with me and my dad with her 2 kids. One of them, the older one, is 12. I think she is responsible and she even gets straight A's every year. She already has scholarships lined up for her. Her mom is constantly being a total ***** to her. She says that shes picking up bad habits of being lazy and irresposible. Obviously from me apparently. I mean come on, really? Do you really have to be that mean? Her mom has never said goodjob to her when she brings home straight A's on her report card. She is a ***** to me and plainly to everybody. She acts as if her life is so hard.. yea right so hard. You pay for nothing because your hounding my dad for all the money you need, suprised my dad can afford to pay for a girlfriend, 2 girls and me. Use to say how broke he was all the time before we even moved intogether.