“Are you a slave?”

Keep asking this question whenever you see her watching YouTube.

If she doesn't answer, keep asking in a calm tone.

If she says "No," say, "Don't act like one."

If she says "Yes," say, "Good, at least you realize it."

Part of the attraction of watching YouTube is that one doesn't have to think much, and thinking entails responsibility, which many try to avoid.  Only humans are capable of thinking, but many rather feel, because it comes naturally. Thinking requires efforts.

Get her books to read.  Children's version of the Bible that fits her reading level, not about religion but knowledge.  Yeonmi Park's "In Order to Live."

Ask her to feel less and think more, and develop a reflex of thinking.