Last night, I went out to a cool bar in a hip part of town to see my best buddy play a solo acoustic set. I was dressed sharp, just worked out, and looking to sarge a bit. I got there and watched him for a bit while nursing a beer, as I was the first person who actually knew him to arrive. It was kind of early, so there were not really many people in the bar yet. After about 30-ish minutes 2 pairs of girls walk in, and I know that he has dated one girl in one pair, and slept with one girl in another pair (this guy isn't into PU, but he's damn good with women, he just doesn't study and use the terminology).
I walk up and introduce myself to all the ladies and focus in on the pair that contains the one I find most attractive (they are an HB5 and an HB7). I sit next to the HB5 and focus on her in order to build some rapport and gain the attention of HB7, which ends up working. After awhile the 3 of us are having awesome conversation, during which the HB7 says she's a dork and likes anime. I'm not an anime fan, so I use this as the perfect reason to tease her and she starts getting really flirty, trying to prove that her hobby is not "weird," grabbing my hand while trying to prove a point, etc. I couldn't care less either way. At one point my buddy needs to take a break, so he asks if I want to come up and play for a bit, as I am also a musician. I "reluctantly" jump at the chance, and play a few female-friendly ballad-type songs, making occasional eye-contact with HB7, and she blushes and looks away, etc. Golden. A little while later after my friend finishes his show, he sits down with me and the 2 girls who are the only ones left there. Here's where it gets weird...he puts his arm around the one I've been flirting with all night. Doesn't do anything else, just sits back with his arm around her. Up to this point, I had been certain that the HB5 was the one he had slept with recently. Now I was questioning.
After a couple minutes, HB7 gets up to visit the ladies' room, and when she comes back she sits on my left, kind of leaning her legs against me, putting her on the opposite end of the scene from my buddy. It's getting super late and I have to go, so I say, "Hey I want to see you again. How can we make that happen?" She immediately offers up her number, I give her a hug and tell her we'll hook up soon and it was great to meet her. I tell the HB5 it was nice to meet her and congratulate my buddy on an awesome show. The whole night was a blast, I broke out of my shell and had some fun. In retrospect, I am now about 90% sure the girl I #-closed was the one he slept with, instead of the HB5. I felt too awkward to try for the kiss-close, because I didn't know if that would cause a problem between us. However, at the same time, I don't feel bad about #-closing and flirting with her, because he had at least 3 girls in that bar who wanted to go home with him that night, and I don't think there was anything between him and HB7 other than a random hookup. Seddit, first, any tips or critiques on how I played the night? Second, am I a bad friend if I make a move on this chick?

****UPDATE****

HB7 added me on facebook earlier today, so I sent her a text sooner than I was going to. Then she responded to my text by calling me, which seems like a great sign. We set a date for breakfast in the morning, which I figured is good for rapport building (not quite as "I only want to get in your pants" as drinks can seem). So good news there.

I talked to buddy tonight, and he actually responded super favorably. He said he has no romantic intentions with HB7, although he does intend to carry on a "casual sex from time to time" thing with her, unless I want to date her (which I don't), then he'll cut it off. My intentions are basically similar to his. He and I are totally cool with the idea of being Eskimo Brothers for the time being. He even said he was watching me all night introducing myself and chatting up all the women at the bar, and he was silently cheering me on while playing his set.

TL;DR Everything went better than expected!