Thanks to everyone who responded, much appreciated!
She's always worn a helmet to ride, so compliance with that part isn't a problem.
Agree about reviewing the bike handling techniques. She thinks she hit either a large rock or something on the sidewalk. She was riding her friend's bike, which, although similar to hers, it's still not the same bike. So I suspect that didn't help, and no doubt contributed to the accident.
She is active, especially in gymnastics and equestrian events. She has gone off the horse a couple of times over the last 4 years, but it's much softer landing in barn.
Tuck and roll...
Didn't think about the helmet impacting hearing. I used to ride a motorcycle and wore a SHOEI RF-900 full face helmet. They can be hot, but don't think it hampered my hearing or peripheral vision.
Will probably let her decide which type helmet she prefers, as long as it meets safety certs.
Thanks again for all the responses, you gave me a lot of things to think about.
DL