That's great that she has recovered enough to go on the cruise! I'm sure its a relief.
As for the carry on of the O2 equipment, understand that most of the time (if not all of the time) the terminal workers (baggage handlers and security personnel) are not Carnival employees. They work for the local port authority. SO what Carnival claims on their website is the policy of CCL, it may not be the policy of the port security people. I however, would have demanded they check the machine and let you carry it on, I would not have left such a vital piece of medical equipment in the hands of the baggage folks. It could have easily been dropped or broken OR even left behind. None of which would have been a good scenario.
Besides that, how was the cruise?
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013