How to act? (long but with cliff notes)

Hey

I've posted a couple of times about a girl from work. They've all been pretty long posts, and I know that might've made a lot of people skip them but here're the links anyway if anyone wants to read them:
[url]http://www.loveforum.net/t4173-is-she-not-interested.html[/url]
[url]http://www.loveforum.net/t4382-does-she-just-wanna-be-friends.html[/url]
[url]http://www.loveforum.net/t4777-birthday-gift.html[/url]

If not here are some cliff notes that summarizes them: worked with the girl for some time, started talking to her at a company party, ended up sleeping (only sleeping) at her place, took her racing and partied a couple of times more with her. I asked her out but she hesitated and made up an excuse not to answer, then later at another party we ended up kissing but the next day she acted like nothing happened.

I have a feeling this one's going to be pretty long too, but I'll include cliff notes at the bottom of this one too :) Anyway, here goes:

After her birthday where I ended up giving her the chocolate Christmas calendar (which I found out wasn't the best possible gift as it turned out she had gotten a dozen of them already from other people who she also sent the text message) I was invited to the birthday party of a friend of hers, which I only know through her and not very well. As the party was getting closer I was asking her for advice on what to bring as a gift, and then suddenly she says that she isn't sure she'll be at the party herself. I ask her why and she says she won't be able to be at a party with her ex-husband, who will also be there, right now. I told her that she HAD to come, or else I would feel kind of awkward being there not really knowing anyone that well. I wasn't able to persuade her, and I ended up not going. I asked her if she would go to the movies with me instead, but she didn't answer that message before the next day even though we had just sent each other a dozen messages. She said that she couldn't as she already had a boyfriend. I was a bit startled by this and answered that I was sorry, but I had no idea.

After that we didn't really talk as much as we used to. We sent each other some messages once in a while, but it wasn't as before.
All the time I'd had a hunch that she'd been with one of my other colleagues, with who I'm great friends, but I always told myself that it was something I was making up. One day I could smell her perfume on him and that just made it worse. I never confronted him about it though.

Then one or two days after New Years Eve we talked a bit by text messages again, and somehow the evening where we kissed came up. It turned out that she couldn't remember much of the evening but had been told by her friends about us kissing. She told me that she'd been embarrassed about her behavior because she just wanted to be friends with me and felt that she'd screwed everything up. I told her that it'd take more than that to ruin our friendship, and at that point I more or less settled for us just being friends and I actually came to accept us as just that pretty well.
One Friday evening when I sent a message asking what she was doing she wrote back that she was partying and that I was welcome. It was pretty late but I drove to her place anyway and ended up staying there the whole weekend partying with her and her friends, all of us having a good time. I got to talk to her about a lot of stuff that evening, and I found out that I had been right about her and my other colleague but that they were no longer together.

The next week we agreed that we should party again the week after that (I know this sounds like partying is all I do, but it's really not. Two weeks in between the two parties :)). As agreed we meet at one of her friends this Friday and had a nice and quiet evening enjoying some beer. It got pretty late and on our way back to her place where I was to sleep over we fooled around a bit in the snow having fun. The next day we went out eating with her friend who agreed to drive the car home, so we had a couple of drinks and maybe a bit too many. When going home we stopped at some other friends of hers where we spent the rest of the evening talking and having some more drinks. Her friend who drove us there left a bit early as she was going to her boyfriends place. When we finally decided that it was time for us to go home, she insisted that we drove but I told her that none of us was in any condition to drive and took her keys. She finally agreed that we'd walk, but was barely able to. I had to have one of the other people who were there help me carry her home, and on the way while half supporting and half carrying her, she started kissing me. I was far from sober myself so I went along with it, and we kissed most of the way to her place. When we arrived she suddenly seemed to be a lot more sober and she practically jumped me covering me in kisses. We quickly ended up in her bed undressing each other. Then all of a sudden someone knocks on the front door and we hear the door open. We jump out of the bed and she shouts that she'll be right out while throwing on some clothes. It turns out that it's her downstairs neighbors who'd come home from a party, and we sit and chat with them for a while. When they left they barely made it out the door before she jumped me again and we ended up in bed having sex (my first time actually).

The next day when we wake up she asks me how come there’s a lot of stuff thrown on the floor, and I answer that we managed to do that the night before. She acts completely as nothing happened and I think she might not be able to remember. But then again we both woke up naked lying across the bed, our clothes thrown all over the room and stuff from the bed table having been thrown on the floor too, so I'm pretty sure that even if she doesn't remember she should've been able to figure it out. We get up but I tell her that I could use an hour or two of more sleep, and we both go to bed again. After lying there for ten minutes or so I reach for her arm and hold her hand for a while. Then suddenly she gets up, and leaves. I though she might be getting a painkiller or so for the headache (she almost always has a headache after we've been drinking), but then I hear laughter from her living room. I get up; put on some pants and goes to the living room where she's watching Bruce Almighty so I join her. We lie in separate couches so I wasn't able to cuddle. We watch two or three movies, with me sleeping through most of the last one. One of her down stair neighbors comes up during one of the movies and watches with us for a while then leaves again, never mentioning anything about them catching us the evening before even though we talked about them being up when they came home (I'm pretty sure they know, because his girlfriend mentioned them catching us doing "something embarrassing" the evening before). I end up driving her to get her car, and afterwards I drove home. She did seem a bit surprised when I said goodbye, but didn't say that I should stay or anything like that...

Phew, this actually ended up a lot longer than I had imagined. I don't even know the reason for me posting this, but I don't really have any friends who I can talk to about stuff like this so I guess this is my way of getting it off my chest. Should I bring it up with her that we had sex (as I wrote I think she's already figured that one out, and if not, her down stair neighbors will surely mention them catching us some time or another), or should I act like nothing happened? (Reading that question I realize that it's actually pretty obvious what to do, but how do I bring it up?)

And now for the cliff notes:
She tells me that she already has a boyfriend. After that we don't talk as much as we used to. We get to talk the evening with the kissing through and decide to just be friends. Start partying together again. She tells me that her boyfriend was a colleague of mine, which I had a hunch about all the time. We get pretty drunk at a party and ends up having sex (my first time). She acts like nothing happened again the next day. She might not remember so should I bring it up and how?