This kind of behaviour isn't uncommon - it happens all the time. I couldn't even get an apology from a rep from a goddam PR firm for allowing herself into my my car and posting pictures of it on Instagram even though our contract forbid it. I have long pieces of PVC piping that literally say DO NOT ENTER and block the door that people still climb over. If you want to rent your car, you have to be there and you must have insurance.
The dullard that is sitting on your car doesn't deserve your grace. I'd plaster her face everywhere. Social embarrassment is about the only power we have these days when either people or the law isn't interested in what's actually right and fair.