As a follower does she ever change into a werewolf during combat? If so she might be handy in a major "vampire quest" I'm about to go on.

I do not believe she does. Maybe there is a mod for her to, but I have never had her transform.

Are you asking if she turns into a literal beeotch?

AFAIK none of the lycanthrope Companions ever transform with the exception of the scripted scene where Aela does it in the Underforge. According to UESP if you have her as a follower and transform in front of her she may actually become hostile and attack you.

"Turns into"? Lol she pretty much starts out as one of those.

Damn! The Dawnguard and my team are about to take on Harkon. It would've been one hell of a sight to have taken her along as well and for her to become a werewolf in front of him!