From what I gather, it wasn't a forced separation thing. It sounds like it was more of a school club or group that provided black kids an opportunity to meet and discuss topics that affected them. No different than a women's group, for example. After her son's friend started going to this group, he decided he didn't want to hang out with Tafoya's son anymore, or, that he liked hanging out with these other kids more. That's called life. I think I've rotated friends groups at least a half dozen times in life. First neighborhood, primary schools, college, post-college, and now what I call the hockey group. It happens.
If anything, it makes Tafoya's comments even more racist than they appear at the surface. Like her son had some sort of claim to this kid's friendship and time. FUUUUUUUUUUUUUUUUUUCK that.