What will probably come out of this and other incidents is Congress making laws about who is allowed to fly. In the future, to prevent lawsuits, airlines will probably require a doctor's visit the week before the flight, if not the day before, to garuntee that you have a clean bill of health and won't giver other passengers rare diseases or be likely to die. If you have any problems such as a history of heart issues, you simply won't be allowed to fly for fear that you might die on the flight and be able to sue.
And as much as I think that airlines are not supposed to be responsible for extreme emergencies like this (to clarify, airlines are not hospitals and cannot be expected to be prepare to deal properly with medical emergencies. Airlines are there to fly you, not save your life), it is sad that she died, and horrible that they carried malfunctioning equipment. That gave a false illusion of hope. I'm not sure what to think about them refusing at first to give her o2...I'd really like to see exactly what happened, perhaps they were taking some time to watch her and see that she really did need o2 and wasn't just self diagnosing herself wrong? All said and done, they have to be somewhat careful with it, right? Do they carry enough o2 for everyone on the plane to suck on it the rest of the flight? (I know they have the emergency masks, but is that pure o2, or what? And woudl those last an entire flight?) It's a Titanic issue: not enough for everyone so you have to be choosy in whom you give it to, in case there is a more obvious emergency later in the flight.
It sounds like a big mess.