I have to say ... I was shocked & appalled at the season- ending of Seinfeld that aired a week ago. However, I've been thinking ...
OK, so you know how in the episode before the very last episode, Brad(?) said to Susan: "You could do a LOT better than him!" ... and then Susan wanted to go away and think for a while. Maybe she was thinking she really *could* do better than him.
My idea is that she got the Dr. to tell George that she died, just to see how George would react. It was supposed to be a practical joke from her end, and kind of a 'test.' (don't say that's lame of her to do that -- George might do the same thing)
I hope Susan comes back w/ a new boyfriend, and says to George, "That Brad Guy was right -- I *did* do a lot better than you!"
Only thing -- if Susan didn't really die -- why did George tell Marisa Tomei that he had the funeral the next day? Of course, George could have been lying ...