Should I attend my Ex Best friends wedding?

I see this situation as more about seeing someone's true colors. Her true colors came out and I don't care to make the wedding as an excuse. She should have been empathetic, that's what I would have expected, not some sly remark. So now, I'd say you've seen her true colors and because of that I would continue to distance yourself. Whether to go or not I do not know. I imagine you yourself might not know until the wedding day. But because you have a heart and are giving I would say go and be a part of her beautiful day then no hard feelings will be lingering around and you can immediately start to distance yourself afterwards.