Don’t ignore her friends.
Females tend to travel in packs. If they’re out grabbing a drink or just hitting the town, they are likely going to be with their friends. Just because a girl you may be interested in is with her pack doesn’t mean you should call of the strike. The best thing you can is approach the entire group. Don’t single anyone out because that will make her feel insecure and it might cause her friends to feel protective. Become friends with everybody, then gradually direct more and more of your attention to your target.