Whilst I do commiserate your Pals had an issue, surely Pax who are affected in this rather delicate and high area of a safety conscious food situation I would have thought should not rely on any airline food being allergy free, surely?
They do have a web page on this -
https://www.westjet.com/en-gb/special-needs/allergies
as do BA too.
In which case if one is sufficiently worried and affected by food allergy (s) then
take your own grub is a bit of a no-brainer....Or try to order a SPCL meal if one is 100% suitable....