What Mobility says on p9 of the handbook.
“If none of the drivers live at the disabled customer’s
address, or the disabled customer lives in a care home
where a number of drivers have access to the car, we
may speak to you about fitting a location tracke”
Providing your mum doesn’t live miles away and the vehicle is used for your benifit mainly, there won’t be an issue.
https://www.motability.co.uk/-/media/downloads/handbooks/car_handbook.pdf