Your sister is aboslutely allowed to watch it herself in her own time, and now watch it with the family. If she wants to watch it herself because she prefers to watch it in silence and to watch the intro, that's fine too.

It's also totally fine for her to share that opinion with the family.

If you and your parents prefer skipping the intro and to discuss it to explain things while it is on, that's fine too.

But your sister is rude to raise her voice or get annoyed at the rest of you watching it differently.