How do I flirt with this girl when I only see her with a bunch of people?

We are in a club at school, but I want to flirt with her so she knows I am interested. I can't go farther than asking her how her day was/or just small talk. How should I flirt without being too awkward with everyone else there? Also, how can I tell if she is interested. I always make eye contact and smile and so does she. Once I said cya later and she said byeeeee, like an extended bye, does that mean anything?How do I flirt with this girl when I only see her with a bunch of people?
Talk to her alot more...walk her to class.....tell her how pretty she is .....ask her how her day is going and hw u can make it better........if..if .she says ';';byeeee'; as in extended ';bye'; that means she trying to tell you that if ';';that is all your going to do or say to her';';.....so try asking her out on a date or something .....nothing to cheesy or played out like the movies ....but something/somewhere NICE....How do I flirt with this girl when I only see her with a bunch of people?
Stare at her, but not in a creepy way, let her catch you staring and quickly look away, and when you look back up, if she is still looking at you then you smile.