Best thing I ever did was let my 11 year old face the full consequences of some vandalism he got caught at with his friend. I didn't hire a lawyer, didn't mortgage the house to get him out of trouble, didn't make any excuses for him. He went to court, had to tell the judge what happened, pay for the damage AND a little fine and a bunch of community service. When he finished, it all went 'away' and he had nothing against him 'on his record', and he has NEVER vandalised again. (Still drives stupid, though, I think he is about cured of that).
I think she should go to the local police intervention officer and talk to him. They may be able to figure something out or he can give her some tools to help her manage this effectively. And she shouldn't EVER make it easy for him to 'get away' with anything as regards school or the law.