Looking for help with home ownership

Hi, I was looking for some advice please..

My friend is looking to apply for a new mortgage which she currently owns with her mother. The bank have said that her mother cannot be on the new mortgage due to her age (she is 76), however the mother does not want her name removing from the house.

The bank have suggested some kind of legal letter arranged by a solicitor to state that the mother has a 50% share in the house.

Have any of you heard of such a thing or is there something else that can be done to ensure the mother retains her 50% share?

Thanks in advance,

Mac