How to talk to a girl i like when she is with her friends?

This situation is the hardest to do. When i like a girl i want to talk to her and flirt with her and then pop the question "will you be my girlfriend". It is really hard when she is with friends though. It makes me feel way less comfortable since they can just jump in on my conversation with the girl i like. This situation has come up way too many times and im getting desperate for some type of solution to it. When i go to crocker (plaza) i see a cute girl but she is with friends. What is your advice??