I need help

Okay so my roommate and I are not friends (I'm in college) . It is fine with me, we are completely opposite people.

My only real problem is I keep walking in on her having sex. Its an everyday thing. Sometimes multiple times a day. We have a system , she just doesn't use it.

I'm working on a way to approach her about that but what i really need help on is ... Well

They stink.

Like so badly.

I don't even have to walk in on them to know it has happened and it isn't normal after sex smell . It smells like wet old landry and sweat and never-been-cleaned penis.

Why? Why do they smell like this?

And how do you approach someone and tell them nicely that they are making the room hard to be in because of the smell. Especially if you have no idea how to fix it ?

I'm really not trying to be rude. I just really have to focus on not vomiting when i walk into the room after they have sex and I'd like to know why and advice on how to approach it.