I'm not familiar enough with your situation to give you a fair reply. My advice for Hemlock, however, is based directly on his wife's infidelity, and that (plus maybe physical abuse) would be just about the only situation I could think of where I would advocate that one spouse tell the other "I think you should leave."
Now, if one spouse is saying "I'm just not happy anymore; I think we should separate," and it's not what the other spouse wants, and if this complaint comes totally out of the blue, then yes, I do think the LBS should say "Well, I'm not leaving my own home; if you feel you need more 'space,' then you should be the one to leave."
It's been my experience that about 90% of the time, there is at LEAST an EA going on in these situations if the marital objections are coming up out of the blue.
