It's clear to the reader that it's her point of view. It's assumed the reader is a mature social creature who naturally considers context, the speaker, their knowledge, etc., not a credulous empty vessel that just accepts whatever is poured in.
> It's clear to the reader that it's her point of view
I'm not sure how the author is supposed to have any idea that due to "so many [previous] concussions [they knew their] brain could not withstand multiple more blows to the head". A PhD in neuroscience? Maybe it's just pseudoscientific claptrap that seems be being lapped up by other sports fans.
If you actually think your brain had already been damaged, you'd stop doing contact sports immediately and completely, not somehow keep going but fighting harder and faster, Ethan Hunt style. Of course it's amazing that she "can now share her secret"... <rolls eyes>
"Her ferocity was built on a hidden vulnerability" is about as believable as your average Hollywood movie plot. A gripping story to push a new book, that's all.
