You might remember a tale of some minor work-related travails of mine from a while ago, related here, here and here.
It seems the object of my disaffection is acting on the unofficial advice given to her - she returned from Family Leave for about six months and now she's back on it again. During her return we neither spoke to, looked at, nor acknowledged each other in any way. We also went to some lengths to avoid being in the same vicinity.
That's a perfect resolution no amount of mediation could have produced.