This is not a second home.  It belongs to her, in her own name.  We live in mine, in my name.
She wanted to sell it some years ago when it was still in quite a decent state.  A quickie valuation at the time was something around €150k.  The snag came when it became clear that her three adult stepchildren wanted much more than they were legally entitled to under French inheritance law.  Since they are greedy scumbags that were very abusive after the passing of her late husband she was/is unwilling to relenquish a penny of her rightful portion of the proceeds of a sale.  To go ahead and put it on the market in the hopes of a Notaire sorting out the inheritance later would have been a road to nowhere.  Up front costs like for the Diagnostique, etc. waiting to find a buyer, and then at the last minute the offspring refusing to sign the compromis because they were unwilling to accept the offer.  This scenario created the situation we are in.  Now it is in such a state that it is unlikely to attract a buyer at any price which is why she offered it to the commune gratis some time ago. 

She has been in contact with them by email.  They're just not interested and unhelpful.

Mysty might buy it. If your wife is the sole owner, surely the step-children have no say in the sale of the property?

It's not the Maire or Mairie that make the decision on whether taxe d'hab is levied on a property but Les Impots, you should go and explain the situation with them in person, I had to do this over several years, mostly they were unhelpfull but would give me a dégrèvement to get rid of me but I had to go through the same palava each year with another person telling me that their colleague should not have granted me one etc.

Finally I got to see the Chef and she seperated my property into two dwellings classing the main building uninhabitable, I came away from that meeting with a much better understanding of the whole rating system, the valeur locatif, indice de vetustité etc, unlike the underlings she did not feel undermined to impart her knowledge so that I could understand the situation.

A rider to the above statement regarding the Mairie, an attestation from them will usually work wonders with the staff at Les Impôts, my first Maire gave me an attestation de domicile after 3 years showing the date I first occupied the property enabling me to reclaim the TdH that by then I realised I should not have paid.

Une attestation de vacance should do the trick and its worth you giving the Mairie one last try, it will be interesting to see their response to a specific informed request, if they don't play ball then I would visit the Hôtel des Impôts.

OH and I had an annual interview with our bank recently and this subject came up.
Apparently, it is possible to write a legal disclaimer without the necessity of using another agency.

The property that I am (I hope) purchasing has similar family issues, I take confidence that they gave a procuration to one of the siblings to put it on with the agent, that the diagnostiques have been paid for but I won't be getting too excited until the compromis is signed, the story that is gradually revealing itself re the family members from my talking to people in the commune is not the one being painted by the agent but that's to be expected, the truth if it is so would put most people off.

What is ironic is that the family could have saved €7K immo fees as I had found the abandoned property during my own searches on the ground in the early summer and it was my first port of call on my return to try and trace the owners/heritees, when I got there the Immo sign was hanging on the gate.

Probably just as well as I reckon had I contacted a family member direct it would have never got to a sale, this way the Immo could advise them candidly of their real chances of an actual sale and the realistic price.

I suggested that you might buy it because Aardvark had said, "Now it is in such a state that it is unlikely to attract a buyer at any price which is why she offered it to the commune gratis some time ago."