some councils have also placed a moratorium on right to buy, and apparently, they have to power to do this even to existing tenants, so double check.
and yes, it has to be in her name because not everyone in government is an idiot and they realise people would do this for their parents in order to get hold of a property on the cheap and get the state to pay for all the elder care.
another reason why i'd never buy an ex-council house.
My friends did this. they paid for it but the house was in her Mum's name. I think she then sold or transferred it to them a couple of years later or something like that. Sorry don't know the full details, I suggest you get some legal advice