I don't know the answer to your question, but here's a resource that should help:
Disney Cruise line FAQs for Guests with Disabilitities.
If I typed it all in right, it should take you to the Disney page. If it doesn't, then go to www.disney.com and type cruise and disabilities into the search.
Also, you should contact her current oxygen supplier. They may have a company that they work with in Florida.
Check out the websites below for info on travelling by train, plane, ship, etc. while on oxygen. My Mom has been on O2 for about 2 years. About a month after she was put on oxygen, she left on a cruise (this was planned well before she knew she would be on oxygen). We had to learn a lot in a short time and it adds extra expense to the trip, since this O2 is not generally covered by insurance. Also, she was flying to the port, so she had to change airlines at the last minute (her original flight was on an airline that does not offer medical oxygen). Also, depending on how dependant you MIL is on O2, you may need to arrange for oxygen service before/after the cruise (or if flying, you may need to have O2 delivered to the airport for a few hours). My Mom's Doc is okay with her going a few hours without it while waiting on the ground. Good luck!
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