Is OTHER wrong in the post ? POST : I'm at the bar hanging out with my other friend minding my own business, and he sees (girlfriend) kiss another guy from across the bar. At the time, he had a girlfriend for about a year. He said, "Yo aren't you good friends with (boyfriend)? I just saw his (girlfriend) kissing that dude from across the bar." He said if I saw his girlfriend doing that to another guy, he would want me to tell him. I had no clue what I was going to do. I didn't really think it was a huge deal so I went up to (girlfriend) at the bar to figure it out.

Next, I go up to the girl and she continually denies it. I tell her I'm going to tell her (boyfriend), and she pins her entire friend group against me. I was honestly on the fence about bringing it up to the (boyfriend), but I received infinite FaceTime calls from her friends. I finally answer, and it's about 15 girls bitching at me, all denying the fact that she was kissing this dude. This is what pissed me off the most, so I FaceTime my buddy and tell him about the situation.

Eventually, (boyfriend) and (girlfriend) start talking about the whole thing, and the (boyfriend) completely takes his girlfriend's side denying that the situation even happened. At this point I'm like holy fucking shit, this girl is such a manipulative fucking bitch.

Finally, the girl ADMITS the fact that she was kissing the other dude, but claims that it was not a big deal. Well, yes, I agree, maybe it would not have been a big deal had you not consistently lied to everyone around you only to admit it in the end. I'm in the middle of this whole situation, and they finally make up and they continue to date.

These girls all used to be some of my good friends, but none of them will even look in my direction at this point. Whenever I would see (boyfriend) and (girlfriend) out, it would be the most awkward thing. Basically, a situation that was not even a big deal to begin with blows up into this huge ordeal.

(some background on relationship with my buddy) We were roommates freshman year in college and joined different fraternities, but still great friends. This is sophomore year now.

All of (boyfriend)'s friends take my side, saying why would he be doing this for no reason at all, explaining how I wouldn't put myself in the middle of this for no reason at all. They explained how some of my best girl friends hate me now, and they all essentially take my side. I think this is what led (boyfriend) to finally break up with her.
Eventually, (girlfriend)'s friends forget about the situation, and everything goes back to normal with them. (Girlfriend) actually wants to kill me at this point, and she still holds this against me (junior year). 

I feel like the biggest asshole because of this, but I just don't know if it's even my fault to begin with. AITA?