Goliaths (Jewfish) get big and yes her head would fit inside it’s mouth but if you watch them long enough they all yawn every once in a while. It sounds like she was just in the right place at the wrong time.
Goliaths are protected but even other grouper I can’t eat anymore. It would be like eating the family pet, they come over to get scratched and petted and follow you around on the reef like a dog. In Fiji I had a 4’ one that would meet me on entry every dive and stay with me until I exited.