Hi @DanCetCol
Hello and welcome 
The other have said most of the pertinent stuff
To summarise and maybe extend a little: It takes a great deal of effort to recover that is not discernable externally - You might do an internet search on the topic of ‘spoons’ Here’s a pdf
Any movement is good. Stroke recovery is a marathon not a sprint so don’t worry about the first few weeks - But you are partly right to talk about muscle wastage BUT much more significant is that this is the time when habits that favour the strong side will develop that will have to be undone later If a more complete recovery is sort.
In my experience the NHS does not have any mechanism for fitting people’s personalities - something that is crucial in personal services of which physiotherapy is definitely one. I would talk to the ward sister or management team about reassignment but don’t hold your breath - I would suggest she/you are better off self-curating exercises than using spoons dealing with a unpleasant PT.
If as Roland said your mum is motivated then if you go to the menus of this forum select videos and then look for the red amber or green group these are physiotherapy regimes for the chair bound the semi-mobile and the walking free. If you sign up to the online activities section of the stroke association website and talk to Nicola @online.activities then she can join some group zoom calls that do a weekly exercise class based on these videos.
If you use the YouTube channels that are listed in this post you’ll also see an endless selection of PT exercises. Just find the edge of your mum’s capability has it progresses and select exercises that straddle the boundary
You may well find
[No idea where it gets the idea of 16 minutes read time that might be the whole thread but not the 40 things]
Useful too because it will give you some insight that you probably are not able to discern on your own.
A final thought that is in the above and other people’s posts but not explicit is be there to support your mum is important while being there and pushing her can be VERY counterproductive - there’s a lot you’ve can’t see within her head about emotions, learning to live in a body where the automated and manual controls no longer work, and a lot more you’ll only discover if you read it a few hundred or thousand posts on here
Give her a hug and think how lucky you are she’s still here
Ciao
Simon