◊ I gave up on the anime because I didn't like the art and whatnot, and I'm still waiting for more manga updates.
I couldn't give you a real answer because I have nothing to back it up with. Sorry. : /
Check out the novels to see if a distinction is made.
In the later episodes, it's implied that Dogkeeper is a girl when the baby called her "momma" and the scene with the Official feeling up on her. As for novels and manga, I can't say. Since Nezumi has shorter hair in the novels later on, it could be vastly different.