Sorry to hear about you mom and good on you for trying to steer her away from the crazy.

You can retrain YT's recommendations by going through the suggested videos, and clicking the '...' menu on each bad one to show this menu:

(no slight against Stan, he's just what popped up)

click the Don't recommend channel or Not interested buttons. Do this as many times as you can. You might also want to try subscribing/watching a bunch of wholesome ones that your mum might be interested in (hobbies, crafts, travel, history, etc) to push the recommendations in a direction that will meet her interests.

Edit: mention subscribing to interesting, good videos, not just watching.