as a parent you need to stay out of it. My DD is the starting pitcher and plays SS for a top regional national team. this was her freshmen year last year. Her HS coach told her she is to short to pitch and play infield she's 5'6" throws 60-63 spins. she sat in the outfield and had the highest batting average on the team. he kept trying to use her as an example of how not swing the bat. the guy is a meat head. it was really hard, but i just kept my mouth shut all spring. good luck and have very low expectations.
Wow. 5'-6" isn't even considered "short". That coach made it very clear that he has no idea what he's talking about, and has unjustified prejudices. Adjust accordingly.
You could pile him with examples of girls shorter than your DD who have been successful at the highest levels of the game, but it probably wouldn't do anything to change his mind.