(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.