Man, I'm not a big fan of all the pua terms.
Gotta learn patience man. Sometimes a post will be answered in a day or two.
Well, fist of all, if the friend is still being a cockblock, then you didn't win her over.
You say that you negged? WHy?
Personally, I almost NEVER neg a girl. I only do it if they are snooty, stuck up, or something similer. If you're out and the chick is cool, I wouldn't try nrgging at all.
You say that the friend was in control? Elaborate. In control of what? Herself, her friend, the interaction, etc.?
I'm gonna tell you something that is very useful for daygame.
Unless you made a VERY good impression, number closes are useless. Seriously, forget about the number close. Go after the date close (I don't even know if there's a term for this xD). Set up a date or "hangout" time and place. THEN get her number just in case she needs directions or something. I find that this lowes the flaking rate by a lot.
There are lots of ways I could approach this. I'm gonna give you a really simple opener and isolation.
This wont work on the girls that you already tried. It has to be girls you have never met before.
Ok, you spot a group of 5 hot girls walk by. You like girl #1. Walk towrads her while holding out your arms as if you're about to give her a hug. Before you reach them, say something like, "Hey! It's been so long. How's it going?"
SHe'll ask you if you've met.
You'll say, "You don't remember me?"
She'll probably shake her head.
Then you isolate her by saying, "So you don't remember me... *Grab her hand* Well let's catch up then. Maybe I can jog your memory." This is where you tell her friends that you're going to steal her away for 5 minutes and proceed to lead her away (Leading with the hand that's held onto hers.).
See, this is so easy because you don't have to win over the group or anything really. It's about a 30 second group interaction and the rest is 1 on 1.
Anyways, that's what I'd do. I wouldn't use that for a chick walking alone.
Also, one more thing. Stop thinking so much about your approaches. You say that you want to kick yourself because of ONE bad approach? Nah, man. Just forget about it. Learn from your mistakes, improve, and move on. If you keep taking approaches too seriously, you wont survive in the PUA world.
Goodluck!