Context:
I moved in with my grandmother last year to be a full time caretaker (she has dementia). When that happened, my mom took my grandma's car keys and gave them to me, and told me I'm not allowed to give them back to my grandma since she's not a safe driver anymore. Her driving has been going down hill for years (as in, me in the passenger seat literally yelling "the light is red!" and "grandma get back on your side of the road!" etc.). She got into two accidents last summer which was the impetus for my mom finally putting her foot down and taking away the keys. My grandma was really mad about that, yelling and demanding that I give her back her keys, but I didn't. The DMV also sent her a letter saying she needed to get retested or else they would take away her license, and she decided not to go so they sent her another letter saying her license is officially revoked.
Problem:
Recently, my grandma has started to search my room for the keys when I'm not around, so I've been keeping them on my person at all times. She's also tried to stick her hand in my pocket and grab them, once she was actually successful since I was wearing loose pants and was distracted, but luckily I noticed quickly enough to grab them back out of her hands. She's also started to tell people that I'm being mean to her by not letting her drive, and that I took away her driver's license (not true, that was the DMV). I'm worried this might escalate to her calling the cops.
Questions:
The car (and therefore the keys) technically still belong to my grandma, so am I breaking the law by keeping these things away from her?
Will I get in trouble if she decides to call the cops on me, saying that I'm stealing her car?
If she successfully gets the keys and drives away before I realize, should I call 911 or is that not something they'd want me to call over?
Location: Utah