When your W has started rambling on about OM, have you ever said to her (in a confident manner, without changing the tone, level, etc.) that you really do not want to know about OM?
I know that this could backfire and really put any possible relationship she has with him underground. However, the W seems to use you as her outlet for any day to day frustrations she has with OM, no matter how trivial they are.
Would it be worth testing the water, somehow and let her know that perhaps you don't want to hear about what is going on between them. The moment it looks as if you could get into any kind of argument, no matter how small, you would have to back out in a hurry.
I wonder if she is not surprised herself that you listen to the bits and bobs she tells you about OM, but don't seem to have expressed any type of disapproval. Or have I missed that part?
You can't do that when you are in her house, but when you are in your own place and start to pull away, maybe it is the time you could let it be known that you are not prepared to listen to any more about her and OM. No sarcasm, no ultimatums. Don't give her any reasons either. Surely she can figure the reasons out for herself.
It sounds to me that you are the only one she is confiding in about OM. By letting her know that you don't want to hear it any more, wouldn't it be possible that she will start to realise how ridiculous her fantasy is? Also, by letting her know that you don't want to hear what he gets up to, could let her know that you are really preparing to move on.
It seems, perhaps to W as well, who may be using it as some form of security, as if you are waiting for W to decidedly finish with OM before you start to make a come-back. By letting her know that you don't want to hear about OM, it could be interpreted as you not planning to make that come-back and W losing that security.
Of course it may make her self esteem and depression worse, but I'm sure your W really has to hit rock bottom before she starts to come around. Perhaps it will all make her less attractive to OM as well.
Could be completely on the wrong track, but it could be another shake that your situation needs.
By the way, one criticism my W had of me a few months ago was that I was far too analytical with our own situation and should just let things be.
Me 44 W 39 M 10yrs (together 13 years) one D 8 ILYBINILWY Feb 2007 Separated - 5th September 07
Will get there in the end. Will get there in the end 2.