Can I legally drive parent's car once they are on Medicaid?

My number one question would be about her insurance policy.

Do you want the car? Can you purchase it from her?

You really only need to drive a car about once every 20 days or so to keep it in running order. Using for a daily driver with that reason isn’t going to fly,

buy the car from her...or sell it. Use the proceeds for her care.

this could be a real problems for her and you. Just sell it.

What we did (because there were other siblings with teens) we bought my MIL's beater van for $500 (it was a 2000 Ford Windstar, so not worth even that much) for my high schooler. We bought it for cash but still changed the title so that everything was transparent with the other families. We put the cash in her Resident Trust at the NH. She is on Medicaid. If your parent's car is worth more, it may be a different story legally.

Also, if your parents give you permission to drive it, I'm not sure why it would be a problem. Who is paying for the insurance, repairs + maintenance?