Depends, some girls will do it with 2 guys, but only one of those guys will penetrate her, the other one will get a blowjob/handjob. I guess a girl like that just wanted to try something different or whatever, she's not a whore in my book.
But now let's say a girl with 2 guys with DP and shit, I dunno that's kind of whorish.

I would seriously never be able to have a threesome with my gf and another guy, it would end badly.