I've been out of consumer finance for a while now but I seem to recall that in a private sale, so long as she bought in good faith, the finance company can't take the car away, but she can never sell it either as she doesn't have good title.

Buying from a trader, the finance company are entitled to take the car back leaving you to pursue the trader for your refund.

Someone n here will have more up to date info than me though.