I think the mags are available online aren’t they? If that was motability’s direct answer to that question then you may be able to argue the same situation – as the main or only carer, you need access to the car at all times in order to fulfil your role as her 24/7 emergency on-call care provider.
Link to online mags – https://www.motability.org.uk/about/lifestyle-magazine/ – sorry but I didn’t make the time to go through them looking for the specific point but it may well benefit you to…
"Man is born in freedom, but he soon becomes a slave, in cages of convention, from the cradle, to the grave."