Yes, please remember not to take the aliens too literally. They almost ALL have to rewrite history in order to justify what they are doing. The better the marriage, the harder they have to reach in order to justify it. I've seen it so many times over the years on this board. One woman's H was leaving her because she was "too fat" - at 5'8" and 120 lbs.! One H was leaving because his feelings were hurt by one innocuous comment his wife made 8 years ago. Etc. etc. etc. The better the marriage, the more absurd the explanation.
I'm sure you can look through your files and find loving cards and mementos from years ago that prove she DID love you.
But what she is telling you is, she's had depressive episodes before and is having one now. During those bleak times, it FEELS like she never loved you - because SHE can't feel it right nOW.
I'm not saying you should wait for her - that's strictly a personal decision. But don't go away feeling as if the last 20 years have been a complete lie, because they haven't been, no matter what the alien spews.