<human>: So there's me(f/21), my roomie (f/21), her bf (m/21), and her boss (m/30+?)

Okay so as the title says pretty sure she's cheating on him with this older guy who happens to be her boss. Problem is her bf is moving in with her/us at the end of the month.

They've been together for three or so years now, and she's maybe been seeing her boss for about a month I'm guessing. Thing is, I have no evidence. Only hunches.

He (boss) comes over really late at night, maybe 1 or 2 in the morning and she runs out to see him and is out there for 30min to an hour or so. This just started happening recently and that's when I started getting suspicious. Now, I understand that this really isn't my business, but her bf is moving in with us at the end of the month to replace the roommate we'll be losing. If he finds out while he's here and moves out, none of us will be able to afford the house anymore and I really don't want to move as I love the place.

What do I do?? Both of them are really good friends of mine and I don't want to intrude, but if this ends badly I don't want to be taken down with it. Should I talk to her/her bf or should I just stay out of it? I mean, I really don't have any solid evidence. Just the fact that he comes over late all the time, and one night I spotted them out the window and their faces looked close together but I honestly couldn't see much else. If I were dating her I would not be comfortable with this behavior.

So sorry for formatting or grammar or anything. It's late and I'm on my mobile. I woke up because I heard the dog barking because he came over again.)

Can you condense the text into a few key points?
<bot>: Roomie might be cheating on her bf who will be moving in with us with her boss. I have no evidence and am not sure what to do.