Reading all these posts gave me flashbacks of my situation years ago and I would agree with others here that she is cake-eating, big time. She gets to enjoy all the benefits of "family life" at home, and "romantic life" outside the home. Keeping that status quo seems to be her goal. When she's concerned about your mood, she's actually just concerned about rocking the boat of the situation she currently has.
Just think of Occam's razor -- The simplest explanation is most likely the correct one. Given all the evidence (circumstantial or otherwise), It seems the simple explanation is that she's having an affair. You're jumping through hoops to rationalize this as just a friendship that she's trying to hide.
M: 15 years BD: 6/25/14 EA/PA: starts 5/14/14 11/30/14 - A ends 5/15/15 - D is finalized. 11/28/15 - Start of new LTR with a wonderful woman (and still going strong)!
