alibali

My mother paid for a new car for me so i could look after my sister. I signed the paperwork in order to take advantage of the scrappage scheme, but the payment came from her. I am the registered keeper. I am now having trouble with my tax affairs and want to know how can we show/prove that she is the owner? It seems unfair that something that my mother bought to help her family could be at risk of being repossessed.