Whatever she does next, you could ignore and present a wall of silence, perhaps with one "We've explained our side and what we want to do, there's no point in explaining again." Or you could, as a couple, make a "script" to deal with her.
For example,
You told people I have Bullimia, you know that's not true.
You have lied on other occasions, (pick an example).
You wont compromise on visits. Then blame us for not seeing the children.
You show no respect for our wishes, for example you smoked around our child and have never shown the slightest remorse.
Add more if you need to one, one problem, one example.
The above upsets us, makes it impossible for us to trust you and has affected our health and happiness (or whatever is true). So we don't want to see you for a while.
If she rants, blackmails, denies, keep repeating the script, calmly, but firmly and when you've had enough or feel you are loosing the ability to be calm say something like, "I'm sorry, but we've made ourselves very clear. When we are ready we will make contact and we'll see if we can sort this out together then."
Say the same to your FIL if you need to, but perhaps more gently.
Stay calm however much they jump up and down.
Refuse to engage in text/facebook ping pong.
Either explain same to any friends/family who want to interfere or be nosy or say "sorry, there's a lot going on here that you don't know about and we've had to do what's best for us." Then refuse to be drawn any further.
Your real friends/family worth the title will understand.