Nothing will change that she was speeding. There's no loop hole that says, "If a police officer commits a crime while pursuing you for your crime, then its a get out of jail free card."
You can pursue the officer's actions and make his job a living hell, if thats the route you wanted to go. This is of course if you can prove he did exactly what your girl said he did.
If you can prove that he didn't shoot her with the gun and that she wasn't speeding, just like any other speeding ticket, then you can get out of it. I would have asked to see the radar reading in the car and the log to verify that I was doing the speed he said. The officer might have visually pulled her over for speeding and you can try to dispute this sort of procedure but police officers are visually certified by the state to observe the speed of cars.
Police officer's word > your girls.