Losing my friend, how to get her back?

There is one thing you can do because it's in your control. Target keeping your self respect as the most important thing. Everything else will fall into place. You are not going to win by biting back because there's too much risk of whoever joining in against you. Uncertainty is a "killer" so if you say nothing and just go about your business your "friend" may keep asking what's the matter, test her, leave her hanging.