I hate to sound callous, but the fact that she died from this means there is some form of other issue within her body, or the response by her body.
Germans listed out a group of variables that change your odds: pack-a-day smoker, taking blood pressure medication (some suggestion that blockers may make it harder to breath), diabetes, COPD, asthma, and liver ailments.
She probably fits into one of these categories. Lot of people walking around with a poor or malfunctioning liver, and don’t even suspect it.