The designers' official ruling is that your girlfriend was cheating. But I don't suggest you listen to the designers if you ever want your girlfriend to play games with you again.
I've ranted against this before. Dumbest official ruling ever.
This was never part of the original design of the 1980's GW edition, Dracula could (and craftily did) double back at will.
Personally, I can't see the need to change, especially when there was an extra Hunter added. I'd suggest just deleting that rule entirely.