I was gaming this girl with a boyfriend, which wasnt a big deal because it turns out that I didnt need to run any BF Destroying game because someone else has already destroyed him...his best friend. His buddy is fucking her behind his back, and she invited me to her grad party where I will most likely run into the Boyfriend and the best friend of the boyfriend.

How can I come out on top (of her) in this situation?
What can I do about the best friend?
What techniques should I employ at this party?
If I get to direct with this girl do you think guilt of cheating on her boyfriend with two guys will ruin it for me? If so, how should i go about it?

Bumping, because I want all the help I can get.

What exactly do you want out of this situation? If you just want an f-close, you can try but expect a shitload of drama. Those two guys will be stuck on her like glue, especially the best fiend. You'll be lucky if you get 15 minutes of private conversation with her all night. If you do want to take the risk (which I doubt if she's worth), your best bet is to make plans to meet up another night when her other 2 lovers won't be there.
And if for whatever reason you want her to be more than just a fuck, then you are out of your f-ing mind.