Oh dear... I'm not liking her behavior at all... taking off the wedding ring, ending sexual contact, staying away longer... This sounds very serious.
I'm definitely getting the "someone else in the picture" vibes. Have you thought about coming out and asking her if there's someone else?
I don't have any advice except perhaps to contact one of the divorcebusting coaches on this site.
Taking off the wedding ring is the worst one... a good friend of mine has been a widow for over 10 years, and this week she finally took off her wedding ring. Anyway, she lost 30+ lbs, and NOW she's too fat for the wedding ring?!?
How did she lose 30-40 lbs in a few weeks? THAT doesn't sound possible... Did she start wearing the ring on another finger in preparation for taking it off altogether?
You say she's been depressed for about a year? What else happened besides the move?