The standard is the standard is the standard! Certain behaviors are acceptable, and certain ones aren't! It's a bit like when women say derogatory things about men and their justification is, "They did it to us for years." Two wrongs do not make a right. That's the second cliche' in one paragraph. I'm on a roll!
It's time to take a deep breath, put on your leadership hat, and have a very courageous conversation with this person. Don't guess about her intent, but talk to her about the derogatory comments you've heard her make about Whites and that those comments are simply inappropriate at work. Also, remind her that making comments that put down members of any group of people is bad for the company, bad for the team, and bad for the image and reputation of the person who said them.
DO NOT go down the 'reverse racist' path. If you try to talk to her about being a reverse racist, a forward racist, or an African American racist you will soon be having a discussion you are not prepared for. I'll almost guarantee that her response would be that nobody who has a history of being historically discriminated against can be a racist. You don't want to get into a discussion about racism. You want to help your friend modify her behavior to be more successful in your work environment. So, do your best and have your discussion with her.
If she can't or won't hear it from you as a colleague, you have to figure out how to take it to the next level—if the behavior is severe enough. You may benefit from conversing with your HR department or senior management before or after the conversation.
Remember, the standard is the same for everyone. It takes courage to get back to the behavioral standard! But it's worth it.
Good luck,