That's one of the basic premise of Group Theory. In most club and bar settings, girls are almost always in groups especially hot ones.
I posted a FR some weeks ago about how I went into a 6 set (4M/2F), befriended the guys, learned that they were only coworkers, zeroed in on my target, and extracted her out.
I did not talk to her at first. I addressed the entire group. Befriended all of them. Learned what the social dynamics of the group was. Physically isolated the girl. Out-AMOGed all the other guys who were trying bust in on me. Then lead her away.
For girls, very similar, but instead of out-alpha/AMOG, you're gonna pay more attention to all the other girls (especially if your target is the hottest one), find out the social dynamics, maybe neg the target, and at a certain point, say "Can I borrow you friend for a moment?" or "Here let me show your friend something." (Credit Mystery and his Mystery Method)