The woman is Valerie Taylor. She is a famous shark handler, with experience on numerous movies (eg Jaws and Orca).
Also, SHE ALREADY HAS EXTENSIVE EXPERIENCE SWIMMING WITH GREAT WHITE SHARKS WITHOUT PROTECTION. In fact she and her husband captured extensive footage of great white sharks using this method, which they released in the movie "Blue Wilderness."
She is also credited with dispelling the myth that sharks will suffocate if they stop swimming (and the related myth, that sharks never sleep).
It is almost as though you are a vacuous idiot and this woman is smarter than you.
Spoiler alert: she's still alive. Her and her husband are shark experts. They're quite crazy, obviously, but they're still experts.
And yeah she probably will get eaten one day, but she's in her 70's, at least. She's probably outlived the usual life expectancy for crazy shark experts.