In need of a little advise, here's the back story:

Theres this girl i went to high school with. She was cute and all, and pretty fun, and we used to smoke weed all the time together, shit was cool, I didn't really much more than a friendship (hopefully to get physical) while maintaining a great friendship we had. She has had a history with a few dudes and is sometimes seen by others as a slut. I didn't care how many dudes she was with, she was good company.

ANYWAY, after grade 12 finished and we hung out more, we were both at a party, very drunk when I simply asked "Would'ya wanna go to your tent?," which is a little odd for me being a shy, self-conscious guy with little to no physical experience with women. Being as intoxicated as she was gladly accepted.

One thing led to another, I fingered her (looking back, here may have been mistake one), but I dont think it went too well. Doesn't matter, we still continue to hang out. At the time I was sure there was more to come but I made absolutely no advances and justified to myself that she was experienced and if she wanted it, she'd come get it, right? I see how stupid that frame of mind is but thats how it was playing out in my head. Months pass, we're still good friends, and I introduce her to one of my 'good' friends Sam. Now Sam, like this girl has quite a bit of sexual experience and finds getting closer with women much easier. Again, this didn't matter I had an awesome friendship with this girl, which I somewhat hoped would grow.

Now after about a month Sam and this girl get more physical. I'd drive us to her house to go into the hottub and usually end in a movie or something. The two would always end up kissing occasionally, wrestling, cuddling etc. Now it wasn't just me there, her friend who didn't want to get physical (as I wasn't interested either).

After a couple times of this happening, I tell my buddy Sam that I'm sick of driving for him to hook up with a girl I like, and all he had to say (he wasn't interested, half asleep) is "Man, what do you want me to do, I think she likes me" so I asked if he likes her, and he said "Nahh man but what am I supposed to say, no?" So after a moment of silence I drove him home.

About a week or so later I left for a week long vacation, quickly upon arrival, I find out they fucked and whatnot, making me feel very shitty. At this point I lost all my confidence, felt like a plain loser, and was just sick of everything.

Months pass, they're still going at it in an open relationship (basically what I wanted to share with her in the first place), and both friendships with her and Sam have gone to the shitter. They're basically a couple and I feel outcasted.

Should I talk to her or cut it off?