That will make it tougher obviously.
One thing you might consider is doing the e-learning then planning a trip somewhere to do your checkout dives.
https://apps.padi.com/scuba-diving/elearning/
Typically that will require 2 days to get
certified at a minimum because it's 4-5 dives and you can't do them all the same day,
Given your situation, it will likely take a couple more days to figure out the adaptations needed. But shops do it all the time - a guy from our shop is a permanent paraplegic and he dives - he uses webbed gloves to move. A woman in my group is a certified HSA buddy - she's not an instructor but accompanies special needs divers and provides assistance in the water as needed, She actually goes thru training with them. . .
It's not close but the Florida Keys are easy shallow diving that you could get to without int'l travel. Shops there would rent you just about everything needed but it's suggested to own your own mask, fins, boots, snorkel to be sure it fits. You don't want to be fighting gear problems while concentrating on learning to dive.
From Miami or Ft. Lauderdale there's reasonably priced shuttles that will drop you directly at Keys hotels - some in Key Largo like the Holiday Inn have reputable dive shops on site - actually I think there's 2 there on either side of the marina. It's pretty much all boat diving so you may as well stay close.
The MS/ventilator diver I mentioned - he dove with Conch Republic Divers in Tavernier. I wasn't there but saw the video - they put a ramp on the boat and helped him board then went to a shallow site and helped him dive.
Check Amy Slate's Amoray also - it's all on site there. One thing to check also is access - I've been to resorts in FL where everything between the buildings is sand so tougher going..
I might bypass your local shop unless you can work out something. And I wouldn't learn in cold water unless you have to - the buoyancy characteristics of all the gear are different. Your sis might have problems with the stiffness of the wetsuit also - the thicker needed the stiffer.
Start with Diveheart - they deal with these sorts of issues daily. Or have resources in your area that do.