Very rare i guess but it happens. Even very young people sometimes die (>200k per year in the US) of sudden cardiac arrest for often no particular reason while being completely healthy.
Sudden cardiac death is different from myocardial infarction (heart attack).
Sudden cardiac death in younger people/athletes is usually due to hypertrophic obstructive cardiomyopathy, a congenital defect. In older people it is usually due to ventricular arrhythmias, which can have their own etiologies.
Death resulting from an MI is typically more gradual, usually actually from complications of heart failure b/c the heart simply can't pump as well.
Yes, my point was more about that sudden deaths happen in our society and sometime even our advanced medical possibilities can't really do something, probably was not clear enough.
People of her age and stature, on the other hand, suffer cardiac arrest from rather more predictable causes.