my brother got a DUMB girlfriend

I cant stand her no more. she just get on my nerve. with all the stupid thing she does. and the way she treat my brother is bull. my brother is 19. she treat him like he 1. he not allow to watch tv. without her saying he can. he cant play the game leave the house get on the computer. he work all day and almost all week. his checks be like 600. he get maybe 40 . the rest go on her and bills. he cant even spend his own money. if he buy something without her telling he can. she throw a fit. screaming at him and everything. I DONT SEE HOW HE CAN STAND HER. she cheat on him and everything. my whole family try to convince that man that he would be better off leaving her. he just dont listen. I really need a way for him to see the truth. she even think she apart of our family. HA we dont even like her. she alway going around saying that she mz.hedgecorth. she got life twisted. if she think she is apart of our family. someone need to stomp a hole in her. like 5 min ago me and my brother was sitting on the couch* ( it barly enough room for 2 people). here she come she just flop down right between us ( very painful on me). made me drop all my food I had. she didnt even say sorry. UGH! she recking my nerves. ill end up slapping her or something. what is a way to make my brother see the truth?