the 4 week rule is rediculous and should be extended to 3 months as 4 weeks is nothing in the way of an accident, especially for old, frail or disabled folk.
sorry to hear your mum is in agony, and hope she can be helped in rehab… alas i think unless the stay is only just over by a week or so the car will likely be returned. dont hold your breath for a good price from motability.
Current Car: Hyundai Kona Premium EV...2 way 40kg hoist
Last Car: Toyota C-HR Excel Hybrid...4 way 80kg hoist