Most insurers insist that the policyholder is the registered keeper AND the owner. If you do what you suggest then the insurance would be completely null and void.
I suspect in your case it already is as you are most likely the real main driver of YOUR car not an occasional named driver.
Pulling the wool over insurers eyes is never a good idea. They know this scam, and many more you do not know, very well and are looking for it as are Police when they stop young drivers.
I suggest you read the links below and see what trouble you both could easily be in as both you and Mum are committing fraud -