I have to agree with others. Call the dealership and ask for the motability specialist. After, take your mum with you as it IS her car, so she needs to be comfortable getting in and out. The Škoda someone mentioned earlier is a superb car, but do look at multiple vehicles and when she finds one she gets in and out off, and is comfortable sitting in, then you can perhaps look at test-driving it.
Also just to add, if she needs a wheelchair or such, make sure it can fit in the boot etc… Having a nice car is one thing but having a practical car that fits her needs is critical over the badge.