Be interesting if the copper gets off unscathed, rightly or wrongly, because I doubt the owner of the car she damaged would escape some form of criminal prosecution for that kind of behaviour, if they were restraining her while waiting for the police to arrive. The standards for "reasonable force" are stricter for the police than for the general public, and rightly so, yet I somehow doubt a civilian could get away with sitting on a vandal and walloping them as hard five times in a row.