What if my mother is addicted to web novels?

Your mother reads hot-blooded YA novels, and she gets satisfaction from them. The same way many people get satisfaction from gaming and live streaming. If there is a substitute satisfaction for her, she can put it down.

Giving movie tickets/taking them on a trip/doing square dancing/k singing/senior college. Beyond the world of fiction, there is the love of family. Let her take care of her health. That's what you're trying to do.

Develop her interest in the world beyond fiction.