A ballet teacher or any teacher that favors one girl...?

My dance studio is run by my mom. You would think no one who works their would be mean to me right. Wrong. My ballet and other dance teachers favor this one girl in my class. She is very good and she is one of my BFF in dance but it's not fair that she is always put in the center for all the dances its really annoying and all the teachers say we watch he and we don't what can i do besides sit down with them and talk cause I've tried that and they just told me to shoo and that that wad the way life was. And they denied that they favor her. Please! good advice and no mean comments or ill report you!