Actually, I think I am buying it. I'm normally a big skeptic, but I think I believe it because she didn't immediately tell the police what happened. She told the 911 operator they were playing with a gun. If this was her 'cover' story, then I think she would have been spilling it out to the police when they showed up. If she really was in shocked disbelief at her husband being shot and dead, then her first thoughts probably would have been grief for her loss and not clearing her name.
I wonder if the police investigators checked to see what's in the cd player.