Cut her loose and leave... best thing really. Was married to a guy that was all negativity for 5 years. I always listened and offered suggestions, and yet the bitching and whining continued - with me taking the blame if I tried to help.
You can't fix them... they don't want to be fixed... they 'like' it this way. Makes them feel important if they're world is falling apart - because only 'important' people have problems.
Plus, you'll feel so relieved to be out from under that cloud of negativity. I know I did.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen