What you used to do: Be aggressive and approach her first.
What you should do: Lay low and let her make the first move.
We've established you should not be using cocktails as means of communication, right? And the logical question that follows is, why should she? The answer is, because while you're attempt to buy her affection with alcohol is cliché, her doing so is (unfortunately) an unexpected gesture. But it's that novelty that will work in your favor.
Try this: When you make eye contact with a woman and the interest is reciprocated, instead of bum-rushing the crowd in an attempt to get at her before she runs off, stay exactly where you are, and keep doing exactly what you're doing. Throw a coy smile in her direction, and non-verbally establish interest in any way possible until she works up the courage to approach you.
This might go against typical bar protocol, but it's the inversion of the expected that makes it exciting. Women enjoy the chase, too! Play into that innate desire and you've already set yourself apart—and set yourself up for a drink.