You grew up with Hellboy as his partner in crime. And over the year he had a lot of names for you. Mostly you wore the title of Best friend and fellow agent but this month a new phenmemon occurred.
The FBI had sent over a new cute agent to help out with some missions...and mostly to keep Hellboy in line and all of a sudden Hellboy was telling everyone that you were "His girl." He got a little more clingy and cuddly too. Really wanted you to watch movies with him, or come visit the kittens or train with him...he just really needed you with him at all times...And Abe told you he heard Hellboy talking to some higherups trying to get the new agent reassigned to the Antartica unit...
When you confronted him about it he simply shrugged and blew out his smoke. "What?" He smiled. "You've always been my girl!"