Great, this has been the only sticking point I've had, such as setting dropbox up on the girlfriends laptop just for some occasional code access I don't want everything I have in there to download.
Your girlfriend could just get her own dropbox account and then you share a folder between you. That's what we do with work. We all have our own dropbox account, but then we share a folder between us all and only that folder gets shared to others.
