Well, i'm having yet another 'interesting' conversation with Dah, so i might as well answer my own poll!!
I think it's a combination of everything, but until recently i didn't think it had that much to do with her serve, but she really needs some free points to help her hold more often. The Australian commentators have incredible insight into her game. For ages i was trying to figure out what's wrong with it cause the action itself looks fantastic, but the problem is she doesn't delay the right hand long enough, she needs to stay in backstratching position longer and then explode onto the ball. Maybe a more side on position might help too.
Other than that, i thought she played an ok match against Serena, if she's in a good position she'll still make the right shot, and vamping up the serve might open some more opportunities.
So for me, it's Serve and Confidence.