Thanks all for the replies
Pogre - Yea addiction is a hell of a disease. I'm definitely glad you found a way out. My GF is still struggling majorly as you can tell from my posts. It's so hard because I feel like the person she used to be is still in there somewhere, and I feel like I saw her come back in those months of sobriety. Of course, that was before I found out that her most recent relapse also came with an EA on the side, so now I don't know what to think.
Trdd - I feel like I see some moves towards honesty too, and I do definitely see a lot of guilt and possibly remorse in her words and actions over the last few days. As for how she could have possibly managed to not sleep or get physical with him, even while drunk, it's actually not the craziest thing in the world if you knew her.
-First, as I'll detail in my update, she was basically going over there to do shots and watch tv, after which she would pass out on the couch. That's very reminiscent to how we used to hang out before I stopped drinking and she would often pass out somewhat early into the night.
-Second, She's not a "flirty" drunk at all. She's actually famous for the funny, over the top ways she gets rid of guys that make advances on her when she's drunk. She's more the type trying to wrangle her other female friends and protect them from other "creeps".
-Third, she's always been someone slow to physical intimacy. Even when we got together, it was a long time before she was willing to go "all the way", even though it was pretty obvious she wanted to from the first time we hooked up. And I know this has always been the norm for her - we were both part of greek life in college, where everyone knew everyone's business, so I would have known if it had been different before me.
-Fourth, as I've mentioned before, she comes from a family that was absolutely destroyed by her father's cheating, and she has always abhorred the thought of cheating, to the point where she even gets physically mad when she sees fictional characters cheating on TV. Now I'm certainly not saying that she would never cheat, especially since she was at least close to doing something like that in this case, but I can definitely see it being something she would have to kind of work herself up to in her mind.
Update
I meet her at work the next day and we sit down to talk. She reiterates how sorry she is and that she's willing to answer any questions I have. I ask her when OM first confessed he had feelings for her. She says she's fuzzy on the timeline because of how much she's been drinking, but she thinks it was in early December. I ask if OM ever tried to do anything physical with her. She thinks and then says "once". I ask what happened and she says that OM tried to lean in and kiss her but she pushed him back. I remind her how important honesty is and tell her that I can even get past knowing that she kissed him back, but only if she's honest (I figured if I told her it was over no matter what she would have no incentive to be honest. So I ask again if she kissed him back. She freezes up for a few seconds, then sheepishly nods yes. Then she says "I was drunk and he caught me off guard, but I only kissed him back for a second before I pushed him away". I asked when this was, and she said it was about the same time he confessed his feelings.
I asked why she continued to hang out with him after this. She said it's not the first time one of her male friends has told her that he has feelings for her, which is certainly true. She said she has never had a problem remaining friends with any of them after that as long as they respect the boundary, which I also know to be true. I say "so the entire time you guys are drinking at his place, sitting next to each other, he never tries anything again?". She says no, and that he never tried to cross the boundary again after that. She even says that, shortly before New Years, he even apologized for trying and said that the relationship between me and her was "special". This is actually sort of corroborated by a passage in her journal where she says "he wanted me to have a good time, even if it wasn't with him" (although she also goes on to say that saying that only made her like him more in the same passage, so...).
She says that it was just nice to have someone to hang out at the bar with and drink without making her feel bad about it. She said she was avoiding me because she was embarrassed of the drinking and she hung out at the bar a lot because of the stress of her work and the tense family situation we had at home during the holidays. She says that they just liked to joke around and make fun of people, and hanging around him made her feel "safe" from some of the more chaotic elements; "kind of like you used to make me feel when we used to go out together".
She says that she cares about him deeply, just like she cares about all of her friends (which is true, one of the things I like about her) but that it was never "like that" with him. Obviously I know this to be a bold faced lie because of the journal, but I don't say anything because I just want to see how much she'll share freely for now. And I guess I can see where it would be pretty difficult for her to just say "yea I fell madly head over heels in love with him".
I tell her that I don't want her to have contact with him anymore, to which she agrees without hesitation. I float the idea of crafting him a "goodbye" text together, which makes her feel a bit weird, but then she says she'd be open to it. I also tell her that I don't want her going to the bar they hang out at alone anymore unless I come with her. She jokes that it'll suck to lose out on all the discounts she gets from the bartenders she knows there, but she agrees and says she'll go somewhere else if she wants to drink.
Later on we get home. I tell her I don't mind if she has a few drinks. I actually have a few with her - it's the first time I've drank with her in years. We loosen up and things feel like old times for a little while. We have a good time sharing some laughs and watching some funny stuff. She says that she's beginning to remember things a bit better now that she's drinking, so she goes into more detail about him trying to kiss her. He says they were walking around a park by where he lives while it was snowing. She slipped and he caught her, and he went for the kiss. She says it was "barely a peck" before she stopped him. She said they had a conversation about it the next day, and that's when OM confessed his feelings. She said she was clear that she was with me and wasn't interested, and that he respected the boundary from that day forward, adding that he's actually a "decent, respectable person" and that me and him would probably get along and make good friends if we ever met and if it wasn't for this. Yea, no thanks...
Then we have some pretty intense sex before we fall asleep. She jumps my bones again in the morning, and starts talking about how in love with me she is. She says she's so sorry for making me feel this way and that she'll never do anything to ever make me feel this way again. She just keeps repeating how sorry she is, that I'm the only one, and she'll do anything to earn my trust back. However, I did notice that she changed the password on her Iphone and disconnected her imessages from her other devices. So I'm locked out of that for now, but I'm sure I'll figure out a way to get access again.
That brings us current. Like I said, I see guilt, possibly remorse (not sure), but I still don't think I have full honesty. Most of the events she mentions actually track with what I read in the journal, but obviously the elephant in the room is that she insists she never felt "like that" with him, and I know for a fact that's not true. Also the fact that she now swears that she wants to spend the rest of her life with me, despite me reading all of her dreams of spending her life with OM in her own words. I also think their little make out session was probably more involved then she's leading on. Other than that, I think most of what she did tell me check out, although of course I can't know for sure.
So I guess that means it's time for something like the hard 180? I feel I've already been doing something like that with my sobriety which has definitely helped me be more present and productive at work and at home. These were all changes I was going to make anyway, even before I found out about any of this, so these will all be good things for me regardless. I guess we'll see how she responds.
I also think I have recovered a bit from my initial shock and I'm mentally detaching and preparing myself in case I need to exit this. I've been running through my mind what I would do and the prospect is not nearly as scary to me as it was just a few days ago.
I still haven't brought up the journal. If she starts being distant again or, especially, if I see any evidence of her breaking no contact I will almost definitely bring it up then. But even if she becomes a perfect angel from this point, I don't know if I'll ever be able to go forward with her without bringing it up at sometime.
Thanks again to everyone who took the time to read this and even more to those who take their time to reply. Your support really means the world to me in this dire hour.