Ok bad news first, This happened on private property, yes a school is public access but it is still private property. therefore the statutes that govern driving are non-enforceable, so she did not need a drivers license to be driving nor did she need insurance, so the cops wouldn't have been able to do anything for you at the time. Your going to have to take her to small claims court.

The good news though, the school did not properly enforce it's own parking rules which put you in the wrong lane and allowed her to drive across the parking slots....so sue the school.