Arrrgghh, just reading this I'm feeling angry. My children are NOT allowed to open the doors themselves… it's the LAW in my car. It is my utter pet hate when someone opens their door and bangs it into the car next to it, and/or lets it just rest on it while they get their lazy ars*s out. Arrrgghhhh.
My advice, if it's worth anything… Get the quote, then talk to her & show her the estimate. She says she's not got much money… but I do think she needs to be more responsible, and learn that she could control her children. I would ask her to make a sensible contribution… not because it's revenge, but just so she has an understanding!!!!
People who aren't into cars, just see them as something to get them from A to B. They have no pride about the state of their car. BUT they should not be so ignorant about how other people feel. So ask her to contribute what she can afford, and what she & you feel is fair. I'm really feeling for you.
I once had a kid ride a bike into my new pride and joy, years & years ago now. I was young, and on my own, (on a dead rough estate - didn't fancy taking the kid to his home to argue with his parents!) didn't really know what to do. Cost a fortune to get it fixed. Still feel pi55ed when I think about it now!!!!!