I agree its too close to call. But anyway I thinks its possible that she (or better her front tire) was in front for a short amount of time.Both before and after the line, Vollering has the advantage. How can the photofinish say something different?
Imagine you holding your arm in front of your body and your fingertips are 1 m in front of you. Next to you is a person doing the same but with slightly shorter arms so its only 0.99 meter. The other person is also holding a dumbbell. If the other person pushes hand (with dumbbell) to the front her arm with extend due to the force and some flexible ligaments and will reach 1.01 meter, but shortly after it will come back, like a spring and will be shorter again. If you measure in the right moment the arm was longer, but shorter before and after. Its could be kinda the same with the bike. Pushing it forward, and then it comes back automatically since the centre of gravity is farther back and the system strives to level the disparency.
(The analogous example is not really necessary but it was easier for me to imagine this way)