At my wits end with this woman!

Melissia
My husbands exwife. Argh! She left him, and their 3 kids after cleaning out the bank account. Their son is severely autistic and they have 2 daughters and she left him with $12. 
Then she moved 2 1/2 hours away into her new boyfriends house and didn't tell anyone until the day of the divorce. So hubby has full custody of all the kids and she was ordered to pay child support, which she didn't until it was $5000 behind. 
She was given 7 months to get his name off the car loan. She's never done it, that was supposed to be last September. 
She harasses him via text because she wants to see the kids more. But I have EVERY text she sent that cancels her weekend with them. She averages once a month. Usually doesn't want to talk their son, because she can't "do things with the girls when he's there".
Then says she wants full custody of their son (so she can collect his SSI and quit working).
So recently she told him she'd trade the car in when he signs off on the back child support. HELL NO!
She refuses to accept that this whole mess is because of HER choices. To move. To not pay for a year. To cancel weekends. None of it is her fault in her eyes. 
HIW DO YOU DEAL WITH SOMEONE THIS MADDENING??!