I see no reason why mum paying for lessons would cause impact to your iva.
Obviously once passed you will need to assess your income and expenditure if you intend to purchase a car to allow for insurance, tax and the petrol etc. How will you fund the buying of a car?
Sharing from experiences of dealing with debt
There is a solution for everyone .... Just need to stay positive !
I, too, see no immediate issues, but I would suggest that she pays the instructor direct (or gives you cash to do so) so that there are not any stray deposits showing in your bank account which an overzealous case handler might mistake for extra income. It is easier to avoid that potential problem than it is to sort it out afterwards !
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk