I've seen so many girls over the years just constantly crank down on their velcro strap, non stop, almost to the point that it's a habit. Not saying this is the case here, I'm sure she's still getting used to it. Good luck, hope she gets it figured out.
It is unbelievably rare to see someone or a player who knows how to properly adjust a velcro wrist strap. It will cause a ton of problems catching the ball. Open the strap up, close the glove fully, and then lightly close the velcro strap. 99%+ will close it while the glove is open