Just physically removed them, she still had the original plates in the boot which she refitted when she sold it.
Right, so just for clarity.
You (she) took the private plate off and put the old original plates back on (a Reg that would have died when she put the private plates on). You (she) then sold the car with the old plate on, but with a V5 document for the private plate.
She then put the private plate on her new car (I assume discarding the old plates in the boot) and drove around and got caught speeding.
The V5 of the new car is a different reg to that display on the car so the speeding ticket will have gone to the new owner of the old car.
When they challenge it, it will then become a criminal case because the car will appear to have been cloned.
This is going to become sticky!