What would you do in this situation?

[Miss.September]

I agree with Misty. Start documenting all the things that they are writing in a public space. Don't write to her, it's up to her to figure him out and they may even be a perfect match - you'll simply be seen as a jealous ex who is trying to keep your daughter away to hurt him. Your daughter is obviously old enough to make her decision, the fact that he isn't turning up to mediation is silly on his part, as is openly defaming you. Don't buy into it, continue to be the good role model for your daughter and let it play out.

[Amity]

DO NOT REPLY UNDER ANY CIRCUMSTANCES.

Not at all. Don't. Just print it all out for later on. And don't worry about the girlfriend - she'll be gone in six months anyway.

If the ex doesn't go to mediation - it's HIS problem. Not yours.

Don't stress. It will all work out in the end...