<human>: So I [26M] started hanging out with this girl [26F] about 2 months ago. We've become close friends, spend a lot of one-on-one time together, and I've developed some serious feelings for her. We've been flirty with each other, so I know there's been at least *some* level of attraction between us.

Now, when I realized I liked her, I worked up the courage to ask her out, only to witness some other guy ask her out instead (from behind a window, they didn't know I was there). I've also seen them hanging out together and hugging/kissing... again, without them knowing I was there (not stalking... my office just has a lot of windows). 

Now, obviously I waited too long to ask her out and I fucked up, I know that. But the previous details are important, because for the last 3 weeks I've known that they were dating, but she has kept it really hidden from me. She never brings it up, and the one time we actually *ran into him while we were together*, she told me after he left that, "Oh, AAAA comes and visits our office sometimes because he uses our equipment," failing to mention anything about a possible relationship.

So I guess my question is... what the fuck is going on, and how can I act in this situation to have any future chance with this girl should her current relationship fail? Should I just keep flirting with her as if nothing had happened, or should I just own up to knowing about her dating life?

Can you summarize the given text in a few sentences?
<bot>: I know she's going out with this guy, but she won't mention anything about it. How am I supposed to behave in this weird situation?