This is long but it’s a good story and and interesting situation.

I’ve been seeing this girl for about 5 months now. But our first kiss, it’s always been unclear what we are. In the beginning she told me that there was a guy who she dated who is now on the other side of the country and said that she didn’t want to get too attached at the end of the school year, especially given the fact that she is spending the summer in the same city where this guy is etc etc. Nevertheless, we got pretty close, we were together for all intents and purposes except for we didn’t say it which left me kind of confused. So anyway, last month, on the 14th, she decided to drop by my room, and peeked through my window to find me screwing another girl. After that she broke down into tears and I realized (or thought) that this girl really loved me despite saying all the crap. So I got serious about her, I convinced her that it will never happen again, and I meant it. I was completely devoted to her after that incident because it was only after then that I thought that maybe this girl is worth waiting for etc etc.
For the past three weeks, I’ve been giving her all the attention in the world and things seemed to be falling back into place. We said and did everything a couple does. Every once in a while though, she would mention that she was worried about summer and that we are not going to see each other for three months while this other guy was going to be there and I told her that all she needs to know that I will be waiting for her. All romantic bullshit that was completely genuine on my part.
Yesterday however, we were out to get some coffee and there was no parking so I asked her to run inside and get the drinks and I’ll drive around the block. She left her phone in the car. As soon as I exited the parking lot, her phone started ringing so I reached for it to turn it off to see that it was a text message from the other guy. It read “don’t worry baby, I’m all urs”. My heartbeat just went out of control instantly, I pulled up to a loading zone and went through her text messages and needless to say the text messages both from her and him were heartbreaking.
When she came back I told her I had read her text messages and gave her the car keys and asked her to drive us back. She immediately threw a fit and yelled at me saying “you have no right to read my text messages” to which I replied “Darling, if it’s okay for you to come peeking through my windows at 2 am, it’s definitely okay for me to read your text messages.” She then started crying like there was no tomorrow and basically told me that everything she said to him was a lie because she knew she was going to be around him this summer and didn’t want him to desert her. I told her that I cannot trust her anymore and she should not expect me to believe her. After she pulled into the parking lot, I yanked the keys out of the ignition and walked back to my room.
Later last night, she texted me “you have to believe me , I didn’t mean those things. I’m going crazy here and if you can’t forgive me, come and end my life. I’m done here.” To which I responded “I’ll always love you but I have to wait until you are ready to commit.”
I haven’t heard from her since last night except for little woeful status updates on gmail chat that I have tried to ignore. Now I know that I was the one who slept with another girl but this was during a time that we didn’t even kiss. She came over, hugged me, teased me, and then left. When I asked her what we were, she would say “I don’t know” and the girl with which it happened had been trying to get in my pants since a long time ago and I had been keeping a distance but that night I just could not control the temptation. What I did was a complete accident. In her case, this is not true. She has been texting and talking to this guy, telling him I don’t know what and it makes me feel really frustrated.
My question is, given all of that, should I tell the other guy what has been going on behind his back or do I keep him in the dark. Personally I want to tell him everything for two reasons:
1. To ruin things for her with him for good. She claims she was lying to him anyway.
2. Just as a guy, I don’t want the other guy to be in the dark and think this girl has been a little angel.
What do you guys think?

To add him to the mix will be to let this thing go further. She may be a sweet girl, but as you said she's no angel. I'd drop her, leave him in the dark, and wipe my hands with it. Good luck whichever way you turn.

She's a lying bitch, tell the other guy.

Bitches, they come they go...

Seriously, save yourself all sorts of emotional bullshit and trauma. Find another cunt to fuck.

^ Saturday to Sunday, Monday, Monday through Sunday, yo. Till then just park your drunk ass on that freakin' runway, hoe.

lolk.

Anyway, paragraphs, faggot. Do you comply?

Awesome...For a while I was just saying that because I knew it rhymed nicely...then I remembered all about the 2002s.

That's fucked up. Either way you look at it, she's jerking someone around. I can't see any way that you're not the one getting fucked over, though; if she doesn't want him to leave her because she's going to see him in the summer, what do you think they're going to do during the summer? In the meantime she's cheating on him with you and on you with him.

I would tell the other guy, just because otherwise he might get stuck with her. Poor guy. On the other hand, it might cause even more trouble. I don't know if doing what's right or what's sensible is the right choice here.

Dont tell him, but forget about her.

As Ryko said, find someone else...

i told him. the fucker called me "delusional" and doesn't seem to have any problem with her "relatioship" with me. aah fuck

Murder them both, chop them up and feed them to dogs.

i hate that bitch. never ever get attached to a girl. fuck em and leave em.

lol what the hell

Actually, he's probably just saying that to you but in private they're having screaming fights. That's what I'd do.