She got caught in a “feeding frenzy”. The predators (including sharks) will push a school of bait fish into shallow water and slaughter them. It’s an awesome display of mother nature but deadly when sharks are involved.
Are you just making an assumption due to the presence of three sharks? I didn’t read anything stating that it was in fact a feeding frenzy. A feeding frenzy is really distinct and even fairly inexperienced divers I’d think would recognize that it would be very problematic to get in the middle of that.
Just in case anyone reading this doesn’t know how to spot one, the first sign is a mass of shorebirds circling and diving over a given area of surf or ocean. Bait fish will be jumping straight out of the water and sometimes are actually driven ashore. It’s not always sharks predating upon them but any predator species with teeth is potentially an issue.