My understanding is that these catastrophic events typically leave the victim unconscious before they have much time to suffer. I'm not an expert so I'm prepared to be wrong. I hope that was the case for her. I'm aware it could have hurt, too — I suppose the sentiment is that this wasn't a drawn out, needlessly arduous event of waiting and suffering.
My understanding is that people have enough time to register "holy fucking shit, this is it, I'm about to die" before they pass out.
That's why they archetypically clutch their chests.