<human>: Can you condense the text into a few key points?

The title basically says it all.

Throwaway account but here's some more detail...

Friday night a couple of girls and I [24f] went out to a local bar. This guy [28] approached me and was pursuing me the entire night - we ended up dancing for a bit, made out a little at the bar, then went on a walk. Hit it off some more at his place (lives behind the bar) and upon leaving he came home with me. Mind you, this has been the FIRST time I have EVER brought a guy home...not really relevant but I feel disgusted about it....the last thing I need is someone to judge me for it. ANYWAYS, Monday night (via Facebook) I found out he's engaged (since Dec 26th, 2011)! We live out of the country (been here since January 2012...so he proposed to her RIGHT before he left) from his Fiance so I have never met her or will never run into her...but I feel a responsibility to message her and tell her. If that were me, it would hurt like hell, but I would want to know before I married a cheater and liar. 

I ended up messaging this guy on facebook telling him that I knew and was disgusted and that he owes it to his Fiance to tell her what happened, and if not I would. He texted me this morning asking if we can meet up and talk. Not sure what he has to say, but we'll see. It amazes me how EASY this was for him though...makes me sick to my stomach.

I've been on her side before - being cheated on - and it's awful. I think that's why I feel I have to tell this girl. Most of my friends agree but a few say stay out of it. 

So reddit, what do you think? Any stories about telling the person or not telling them? How did it end up?

Note: If I would have known he was engaged I wouldn't even had THOUGHT about even DANCING with him....
<bot>: I [24f] had a one night stand with a guy [28m]...only to find out he's engaged. I am conflicted on whether or not to tell this girl.