Frankly, OP, I read the title and thought to myself holy shyte that's cringe AF.
Are you in the US? Are you a native English speaker? My gut says no.
There are other ways to approach it - how about finding a way to be in her vicinity and say something like "That's a great dress". Gauge reaction, proceed. That or find something she's doing, offhand react to something she's saying with a witty side comment that isn't creepy, and get the venue you're at on lockdown.
Befriend the bartenders - every time you're there, tip super high on the first drink of the evening, hand it to them directly, and say "thanks for the awesome service" - tip regularly from then out. Become a regular and do it every time. The bartender, whether male or female, will start noticing you, serve you first, pour you stiff drinks, and act as a source of information, and will wing for you in most cases when you bring a woman to the bar or they notice you're with someone.