I think Karen's is the best suggestion...if they want attention, go ahead and give it to them. Ask the person to stand up for their moment of fame and have the bar applaud them...or have the bar stand up and point to her so that everyone knows who the comedian is ("ladies and gentleman we have someone with us tonight who has a few words of wisdom to share, to make sure that we can all gain the most, let us all stand up, focus all of our attention on our visiting sage and grant her a moment of silence wherein she can drop her pearls of wisdom...if you please madam - begin"). If all that fails ask the manager to cut her off or remove her. Insults will often make a heckler more belligerent, and the legal ramifications of laying hands on anyone is too great to risk simply to avoid an annoyance.