As far as I've read, Mom has not taken the money yet, but it was discussed that the daughter would pay £1k towards the car. Frankly, the daughter, at this age, should have responsibility for her own money; yes, she should always ask for help if needed, but she should be responsible for her own money, that way she would have seen the 1k leaving her bank, it would have had a tangiable effect on her, at the moment she's been gifted a car, all beit paying1k also, but she has not seen that money leave her account, it's had no effect on her, visually or emotionally as it's a completly hidden transaction. So much so, Mom hasn't even moved the money.
Legal owner and V5 are very, very different things, Mom, while I do agree with the sentiment of what she's trying to do, she's really on a sticky wicket.
'We paid £3500 and offered it to DD1 (19) as she was keen to take up driving. She had lessons in the passed but didnt stick at it. So she would have some value we said she could contribute £1000 from her savings'
There are two ways of reading the above, one as a gift it was offered to the daughter, but you could also argue that ownership is shared 70/30 as the daughter contributed £1000. You'd have to know the underlying intent. Gets more tricky ie if they have older children and they have gifted them a car etc you'd have a hard time arguing the offer of the car was not a direct gift.
But are you really going to fall out over a car, the issue is not the car, the issue is the fact you have a 20 year old sat at home who ssemingly sees no problem with living off other people,