I can only see Doomguy being confused by such a non-threatening, friendly demon. His behavior is somewhat unpredictable, but I don't think he'd attack Charlie once he understood her.
Hellboy would almost certainly be no threat to Charlie. He's been around the block enough to know that someone's species doesn't define who they are. He is living proof of that himself.
There are two Dantes here, and the one I think is the least dangerous to Charlie is the one in the red coat. Although judging from the look on his face, I'd say he's got "something" on his mind.
The grey knight is unquestionably a threat, though.

The Grey Knight would likely try to purge everyone in the room.
The Dante on the left worships someone other than the Emperor, the Dante on the right is half demon, and Hellboy IS a Demon.
The only one he wouldn't try to kill on the spot is Doomguy.