I want to know what movie this is but unfortunately the only scene that I remember is a sex scene

The scene is like this:
This girl walks up to this boy and they have their moment and I think she says something like, You are the only one I can trust or something similar. After that they have sex and I remember during that part the girl is quite bossy. Anyways after the make out. This girl wakes up and walks out of the cabin or house. There is another boy standing and she has some sort of disease. So he hands her a knife and tells her to kill him or something. She says I cannot and he yells, he is already dead.

This is the scene I remember and it takes place at night. I remember the actress’s face so vividly but don’t know the name of either boys or girl.