Tango, I think 53-55 is good speed for 13. Is she 12U?
I am in agreement here. the thumbs must be on the ball. Try to tell her to release the thumb on the snap. This will at the very least get her to consciously think about releasing the thumb at "the end of the pitch".
No sir, 14 in April. She pitches for a 14U A class team and is a little below most A class pitchers as far as speed. Movement and location is better than or equal to the better pitchers. Been stuck at 53-55 for a year.