I'm contemplating reaching out to see if I can defuse this before it gets very ugly and unstoppable. As long as I maintain my boundaries, what do I have to lose?

She will see my reaching out as weakness, but that's just her perception. My kids are what's important, and if I can convince her I will negotiate with her in good faith, and cooperate with her as a coparent, perhaps she'll back down, and I can avoid a very long, painful, and expensive process, for everyone involved, including the kids.

She doesn't want to be ignored, so I'll give her what she wants.