We had a situation at an ASA sanctioned tournament a few years ago where the umpires were instructed to ban any player if three conditions concerning the helmets were not met. 1. The helmet had to have a current valid embossed stamp (NOT a sticker), 2. The facemask had to have a current embossed stamp (NOT a sticker), and 3. The helmet and facemask had to be from the same manufacturer.
We had team supplied identical "one size fits all" Schutt helmets with Schutt facemasks. All the helmets even had "template holes" that exactly matched the masks. The only difference was that 3 or 4 were new, the rest were only 1 year old. It was obvious that all were identical - EXCEPT that the older ones had a painted stamp and the newer ones were embossed.
Even a weekend call to a Schutt representative would not satisfy the TD. We wound up having a group of parents make an emergency run to a local sporting goods store to buy 8 or 9 face masks that were embossed.
Safety was not the issue here - no one will ever convince me that this was not some type of racket. But lesson learned. BE SURE of all the minor details and requirements of all the tournaments you are planning on attending. Some will stop at nothing to bolster profits! When they start checking your brand of underwear at the gate, you know you're in trouble!
P.S. As far as vision being blocked, be sure she is getting a good two-eyed look at the pitcher's release point. Video from the pitcher's view will confirm this. Be sure her head is not tilted. Even with good mechanics, some kids are just more sensitive to having something in their immediate field of vision. They have to work harder at focusing on the release point, and ignore everything else.