The timing of her reaction does not appear to be much of an outlier, though allergy studies use vague language like 'usually' because outliers and variations do occur. The studies are trying to find trends, but the ones you cite, and others below all use much of the same type of language.
This source gives quite a bit of helpful information:
https://www.ncbi.nlm.nih.gov/books/NBK538526/
Including, "Symptoms can occur within seconds of ingestion,
with peak occurrence by 30 minutes but can delay up to 2 hours."
Many food allergy studies are conducted with children, but adult reactions can manifest as cardiac events that don't tend to happen in children. -in the Complications section of the above source, so there are even age-related variations in reactions that are not well understood.
Here's another unknown, "There are unexplained regional variations, with United Kingdom and Australia reporting almost double the rate of fatal, food-related anaphylaxis to that in the United States." from this report
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5589409/
At this point, there are many details about this tragedy that we do not know, and some we probably will never know. Perhaps some good can come of this tragedy, like more research, more people making an effort to learn about allergies, and a little more kindness towards those who live with allergies.