It is very tragic and sad. And hopefully she will recover.
BUT again, if her condition is so serious and fragile, why risk a flight. Why effect, if any, might the cabin air compression have on a person who is suffering from swelling of the brain? I don’t know but it sounds like an unnecessary risk, IMHO.
The only reason I can think for taking such a risk is that the care she is receiving in Canada is inferior to that provided in the U.S.
I’m guessing they’re using a pressurised aircraft.