[Por_sha911]

I dealt with this for both parents and in-laws. Lets get some things straight:
-every state has its own laws but as a rule the DMV cannot force a surrender of license. They can require retesting based on certain events.
-Power Of Attorney is NOT the same as Power Over Will. POW requires having them declared incompetent that is very hard to do (to protect civil liberty and predatory children).

You can refuse to be an enabler. When mom says "take me shopping for a new car" put on your big boy or girl pants and say NO! Explain why and let her know if she insists on risking her life and endangering others you won't help her. Don't help her with taking the car to the mechanic. REFUSE to ride with her. Tell her you will NOT get into a car with her when she is behind the wheel.

It will be tough but do what you gotta do. If she's going to drive against your wishes then make it hard for her to do so. There will be the anger, the guilt trip, the cold shoulder. Just like you did to her when you were a defiant teenager. She'll get over it.

BTDT so don't give me the "it can't be done" or "it won't work". It can and it will.