"I would never date a black guy" is not an inherently racist statement. The reason why is what could make it racist. If she doesn't want to because she knows her parents wouldn't approve, that doesn't make her racist. I guess her dick joke comment is playing on a racial stereotypes, but I could also see it just being dick size gossip between girls and not racially charged.

You've said that she made racist comments in the past, but all of you are 17-18, so when exactly is in the past? When you were even younger children than you are now? I'd imagine you and the people reading this comment weren't the same person at age 17-18 as they were when they were 14-16. Holding racists comments she made when she was/still is a child doesn't make any sense if she hasn't made comments recently that still reflect those values.