I really don't see why she even has to act like she's single. Like Piccubed said, if I saw her and she was friendly and wanted to dance/ talk etc, I'd first ask her if her husband was cool w/ it, if her answer didn't sound truthful or I smelled a rat, I'd walk right over to her husband and ask if he minded me dancing w/ her while he played pool/ darts ect. The answer I usually got was 'Hell, no, you keep her busy while I'm playing, I'll be over after a while." I would buy drinks for us anyway, if the guy was cool, I'd buy his too.
Then if your nice to her, dance moderately well, have some manners, I guarantee that she has some friends ( some hawt some nawt) that will be along soon, maybe not that night, but the next weekend, and if she has given her stamp of approval, your gonna get laid like a MF'er....