I wouldn't want to be standing there while two guys get into a pissing contest over my attention.
So, if I was said girl enjoying the conversation with you, I would hope that you would ask me to go to a table, away from the other guy, so we could continue, get fresh drinks, relax.

Show some class, show a protective nature. Don't leave her to fend for herself if you don't have to. A woman loves to know you will be the man, which is diplomatic, charming, and in charge.
Best wishes and good luck!