Well done; you took my advice and applied it knowingly to the context.
There's a bunch of other rules for attraction, but you've definitely nailed one: Confidence. By showing that you don't need to seek her acceptance and kiss up to her buying her a drink (which is not considered chivalry in most parts) you've triggered attraction. The drink is NOTHING. She's there to see you, not to be bought a drink. Some people don't realize.. women get bought drinks all the time. Some even despise it. And I can tell you, at the end of the night, they won't think that you're a jerk for not buying a drink, guaranteed.
You want to be slotted into the LOVER category by being interesting, instead of the PROVIDER category, which buys the woman things she wants. Unfortunately, once you're slotted, it's very, very hard to move into the category, if not impossible. By nailing the formal "first impression" you've secured your category slot.