My sister's daughter (16) sent me a list of movies to download to watch in the car on a road trip.
One of these movies contains a brief sex scene, m rated.

What do I do?

Here are my options so far:
1. You cant baby them forever, and there are worse things than an m rated sex scene, let it go.
2. Tell my sister about it. Shes very likely (99% chance) to not allow her daughter to watch it.
3. Lie to my sister's daughter, saying that I couldnt find the movie.