I am 17 and I am being mentally abused.?

Okay, I am 17 years old and I am mentally abused by my stepmother. She is racist and doesn't let me talk to my girlfriend ( Who is black.) And I'm really derpressed. My school grades have been slipping because of it. My dad says he'd be glad to let me come stay with him. Friends tell me I could talk to my school counselor and get something done. When my mother finds out about me trying these things her abuse gets physical, so please somebody help me!