I am very confused. Why is she not living on the FMH? It is utter madness that you are paying for am empty house and the taxpayer is funding her rent in the same road huh: .
I can understand her attitude towards your new partner especially if she was the reason for the marriage break up. However I just don''t think it is justifiable for you to be bearing this financial burden.
She may not like it but you moving back to the FMH and thus being able to pay cm would seem to be an obvious option. Or sell for the offered price. Her choice.