I let my mum drive my car, and to be honest it is a pain.
As she always moves my seats, mirrors etc, which is a pain to get comfy again.
She changes the radio station, or CD from what i had it on.
She has curbed the wheels
The drivers door has scratches on it, from where she gets out with keys in hand and shuts the door with keys bouncing off the paint.
So if you can help it, DONT LET HER DRIVE IT. If it means you wont get any then obviously you have to let her.
The only reason i let mum drive mine, is cause she doesnt have her own car, she regulaly puts petrol in, helps towards servicing, and tax costs, and she reduces muy insurance by upto £100+