L313,
This may seem harsh, but it is what it is.
Your WW is in a 'no lose' situation for her, as she knows you will be there for her regardless. She knows she will be able to retire with a safety net (hint, it is you).
When someone has nothing to lose and everything to gain, they will not need to do anything, as the end-game is already locked in. They know they are in control and can steer the ship however and wherever they want. You are merely a disgruntled crew in the boiler room on their ship. You will be working hard to keep the ship (M) working, but you don't know where it is headed.
You can rant and rage all you want, demand that she tell you everything, demand that she assures you that it will not happen again, to answer all your questions truthfully and willingly, but at the end of the day, she can choose not to, as she knows she will suffer no consequences (apart from being kept apart from her 'one true love'). She knows she is still in control because she lets you think you have control.
So, for your own sake, you may need to consider other options, or you will have a prematurely short lifespan due to all the stress/anxiety of the unanswered questions. You will not be doing yourself any favours if you will not consider any other options.
Think about it, she had another life that you were not part of for 15 YEARS.
RR