Here are a few I’ve found, not videos, but helpful devices:
Yes, you can knit with one hand! A device shaped like a large clothes peg can be made and clamped to the edge of a table or wheelchair tray to hold one needle. A strip of rubber glued to the inner face of the slot improves grip, and a screw tightens the prongs together. Fasten one knitting needle in the holder and work with the other. When you come to the end of one row, remove the empty needle and insert the full one.
(The illustration below goes with this.)
This, from a “men who knit” forum:
There is a tradition in certain areas (particularly the Yorkshire Dales), of using a “knitting sheath” - a wooden or metal piece which tucks into the belt or under the arm to hold one needle still while the other one works. Looking at examples on Ebay and other sites (just google “knitting sheath”) it looks like it would be easy to mock one up. I’ve heard that there are some specific techniques that are used to work this way, but I haven’t seen a manual that explains it. It’s supposed to be great for speed. It seems to me that it would be more similar to a Continental style, but maybe that’s just because I have trouble visualizing in English style.
The folks we saw knitting in Peru, carried their yarn around their necks for tension rather than wrapping it through the fingers. That might be another helpful adaptation - the left hand carries the tension in Continental. If you’re used to working English, then of course it’ll go in the right hand, but it seems like with the right hand carrying yarn, throwing, and manipulating stitches, it might be too much going on at once.
Hope she recovers quickly!