Don't make decisions out of anger. It sounds petty and passive aggressive to say the "congrats..." thing. I wouldn't do that. Sleep on things, think things through. I'm not saying you shouldn't file if that's really what you want to do, but don't be an a-hole about it. You can always withdraw the filing anyway. But if you do file, tell her with poise, tact and politesse.

She's obviously got some issues she's trying to work out. Yes, it's not cool that she did that around your son. But it doesn't mean that she is a horrible person.

You are angry, and you have every right to be, but don't let that anger control you. You may feel completely differently by tomorrow morning or Monday. Breathe.

M: 40 W: 37
T: 20 MR: 13
S13, S9, S4
BD: 1/29/18
Sep: 4/23/18 (I moved out)
8/24/18 I come home, she moves out

If you want to get out of the hole, drop the shovel.