What a blessing that she's all right!

Just last week I read an article online that reviewed how a helmet "should fit" -

Turns out I was wearing mine too loose. The website said to wear it low on your forehead and tight enough that you can't push it up. I had to tighten it because mine pushed up easily. My chin strap was also too loose. I was an idiot - wasn't even thinking that the helmet serves no purpose if it's not in place when you fall!

So glad your friend is recovering well.