Working it Out?
I spoke to the town council officer about the case with the mother-in-law and daughter-in-law. She seemed like a reasonable and nice lady, and she said that the town council's stance is that this is a family matter which they will not get involved in.
The daughter-in-law also wrote to say that they may ask the mother-in-law to move out. Very sad that it has to come to this, but the relationship may be so toxic that it cannot be saved without a lot of work.