Teens alone w bf/gf

What age do you let teens be home alone with their bf/gf’s?

My just turned 16 year old has been with her boyfriend for a year and a half, generally have a positive relationship and she has an IUD.

I know that I can’t control everything and I’m working really hard to be realistic in my parenting but I just don’t love the idea of them home alone. My teen has the personality of if you allow something once she will ask and expect it moving forward.

I know teens will be teens, I just haven’t parented in a way that provides a ton of opportunity for frisky business. Sure it’s happened but that doesn’t mean you get freedom like an empty house to shack up in.

What’s everyone doing regarding teens home alone w bfs/gfs?