Oh Samson, she's just going to quirk an eyebrow at you before looking at the drink with high suspicion. The last time she was given a drink by someone who wasn't a bartender, she was poisoned and left for dead in an alleyway. Well, then again that typically happens even if she gets from a bartender. So, what the hey, she heartily gulps it down and goes back to eating.

You're going to have to do more than just buy a drink and sit in the same spot, expecting her to approach.