Interms of MLC, the monster is hungry and wants you to feed her anger, she wants you to look bad in front of the kids in order for her to justify her actions in terms of the marriage break up, unfortunately for you she sucked you into her drama and made you play into her trap.
This comment sums it up Her: We will do whether you talk or not. And when you don't talk, I will say its because you are embarrassed by your actions.
What if you said “ok, I’ll pay for the kids activities” . I don’t know your financial situation but if you do that the drama is over or averted. I know in my situation this is exactly what I have had to do.
A positive for you is if she is playing games like this then you should know that you have been playing it straight and it is annoying her, the bad thing is that she’ll keep trying to stunts like this to destabilise you.
Rock situations like this is no win for us, all we can do is what’s best for us and what’s best for the kids.
Always think “avoid the drama” and that will help you deal with situations like this (compassion or no compassion).