How do I take the car keys away when she is very resistant?

Keys won't do her any good if the car doesn't run. Disconnect the battery.

You have to do this no mater how mad she gets. Take an honest look at her driving abilities. Would you ride with her! Or let your kids? If she's a danger to herself and the public by being on the road the consequences are huge. Get the keys or disable the car. She'll be mad but at least she won't kill herself or innocent people.

Do you have POA? If so, you will have to step in and do it, forcefully. But, can you change her keys, so the car won't start?

My FIL was like that, so I sympathize. The police had to be called a few times.