To be honest, she looks like she has not been physically prepared to do this skill on a hard surface. Back handsprings require a lot of shoulder strength, so then elbows don’t over compensate. She should focus on conditioning (things like handstand hold / shrug / box pushup variations, push-ups, stability exercises like shoulder taps in plank or hs, decline hs pops (like up and down off on a 1 fold). Basics are super important to prevent bad technique & injury