I think that we need to ignore for a moment the issue of freehold or leasehold.
Your claimant is a joint leaseholder, and as such has the right to reside in the property, in just the same way that she would as a joint freeholder.
As she has the right to live in it, no rent is legally payable.
John
Annual income twenty pounds, annual expenditure nineteen nineteen and six, result happiness. Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery. The blossom is blighted, the leaf is withered, the god of day goes down upon the dreary scene, and—and in short you are for ever floored.
Wilkins Micawber, Ch12 David Copperfield