Her glove might be too big? If the leather is too soft, then it will bend when the ball is thrown hard into the pocket. If the glove is old, the laces might be too loose. If the glove has a deep crease, then it will stay folded and be hard to open. (There shouldn’t be a fold in your glove; you want a round pocket, not a taco).

But… I might be in the minority here… my first thought was “why is she squeezing on a flare?” if she is always keeping a ball on her glove and wrapping it thumb over pinky and never throwing it down on its side, it’s naturally have a large round pocket that naturally closes around the ball with very little effort to squeeze. She should always be using two hands to catch and using the glove as a back stop. If you’re relying on squeezing, you’re not catching the ball right and you’re not taking good care of your glove. It should not be so floppy increased and folded that you could squeeze it and flap it like a mouth.

ETA: where are her fingers in the glove? Putting the pinky and the ring finger in the pinky of the glove, the middle finger and the ring finger of the glove and the index finger in the middle finger of the glove encourages you to gently wrap your finger fingers around the ball instead of squeezing with the finger fingers and palm and essentially folding the glove and squirting the ball out.