a) a Crow Tribe child apparently has enough autonomy to be allowed to choose where to stay on her own, and b) her tribe is apparently fine with her interest in humans.

Oh, I sort of assumed that it was more like they didn't care anymore. She was too weak to hang with the tribe (for whatever reason), so you know, maybe it doesn't matter what she does. Clearly Ya Qing cared, but maybe not the tribe as a whole?