RAI,
You might want to start a thread over on the MLC Forum and link this thread to it.

My first question to you is this...what, if anything transpired 18-24 months prior to her changes in personality?

The "light switch" doesn't switch off automatically, i.e, the crisis is phased in slowly, but surely until one day they "pop".

You must remember, you didn't break her, therefore you can't fix her. The only person you can fix is yourself. Are there things in your life that need to be looked at? Are there things that you can change about yourself that you will be happy with? Do you have a list of hobbies or a "to do list" that's been shelved for a long period of time? If so, get that list out and start working on it.

The last piece of advice...keep the focus on you and your life.

Sit quietly, the answers will reveal themselves when you least expect them to.
The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.