You can rinse with cold water everyday but theres no for sure way to make hair grow. I would say use false hair to build toplines if its allowed at your fair. Will her hair brush up a bit so you can blend it?
Now this is just a thought, since we're talking Dairy here. As close as that topline needs to be cropped, and tied to the withers, a quater inch right down the middle pulled foreward with tail adhiesive might be about the limit, or risk making it look much worse.