That vault looks pretty good, with potential to work a handspring front, but that's not going to help her stick the handspring vault.
The best tip I can give you is to have her keep her chin tucked in as she comes to the board, and leave it tucked in during the pre-flight. This should give her a slightly lower pre-flight that moves more directly to the table, which would allow her to push off with her body at a lower angle.
The push-off can be adjusted to slow down her rotation by hollowing during the push as if she were snapping down from a back handspring. That wouldn't work for a handspring front, but will allow her to work on sticking her handspring vault, and it would also place her in a good position for handspring fulls. I don't really like the idea of slowing down her leg speed as it could form a habit that's hard to break when it comes time to train handspring front, if thats a future goal.
One other way to go about sticking the handspring is to train her to come on to the table with a lower angle, but instead of teaching her to slow down her feet, have her start closer up on the runway, reduce her run by two or four steps, and just work the skill with less energy by handicapping her run speed. This would have the additional benifit of making her work her run for all it can be, and when it comes time to advance to a salto vault the steps can be added back to her run for additional power.
I've had pretty dood luck with this method. It works so well that I have my beginning and intermediate team kids start their vault practices with a three step run that ends in a rebound to a stand on the table, followed by five step runs that end in a modified handspring. The rest of the practice includes handsprings from a seven step run, as well as handsprings, handspring fulls and tsuk timers from a nine step run. They only go beyond nine steps when it's time to transition to competition vaulting, or to turn a salto vault.
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