I see dead bodies all the time so I could sit in first class without a problem.
Oh yeah- I'm a critical care RN so I'm around acutely ill people all the time and have coded so many I don't even have a guess at a number.
On a serious note- You need a shockable rhythm to have an AED function- that means V-tach or V-fib. If you're in a heart block, PEA, asystole, SVT, etc it is of no use. I wouldn't expect flight attendants to know how to 'save a life' other than basic CPR including use of the AED. Oxygen would not have saved this woman's life. I'm sure an investigation will occur, but their shouldn't be a lawsuit. At least I wouldn't award them damages.