I'm usually the only female in the room at work. "Thanks guys!" Is always fine. You don't have to awkwardly run your eyes over me, then tack on an "and ladies. Lady." Or some variation, break up your train of thought, then continue what you were saying. It makes me feel nervous and singled out, not thanked. We don't have to acknowledge my vagina, and point out that I'm a little different from everyone else every time the group is addressed. I'm already having to fight misogyny. Calling everyone else "fella" while you call me "girl" is not pleasant.

Edit: Lots of people debating if "guys" is gender neutral or not. See the 1st dictionary entry here.