It depends, like the others said. How long did you date? How long ago did you date? Hell there are a few chicks I know that got passed around to almost all of us.
It would bother me a little, but it would also depend on the friend. If it was a girl I cared a lot about, and I know my friend will treat her right, I have no choice but to have no problem with it. But if he's just gonna use her and abuse her, then yeah, that's fucked.