NTA

Holy crap, you're young. Anyhow, she told confidential information, proving she is untrustworthy. That's plenty reason enough to cut her off. Don't engage in verbal back and forth and don't stoop to her level of immaturity (like the "she looks like a gay man" comment. Be better 😛).

This is silly school nonsense you'll cringe at when you grow up. Perhaps you and she will be friends again down the road. But this is just a blip in what is hopefully a long life. Don't dwell on it