She doesn't understand why anyone would want to waste their time making themselves feel miserable. (Which, to be honest, is a legitimate point: why are people drawn to movies that they know will be sad and depressing? I think that's a deeper question than I'm prepared to answer at the moment.)
At any rate, I was trying to tell her about the beauty and humor in one of these last-potato films, and we came up with the feel-good romantic comedy, Another Potato, wherein a young couple, after much hand-wringing over who should eat the last potato, finally decide to share it. They have reached the pit of despair, and the realization that human suffering knows no bounds. But in their wailing, they find that there is another potato! It is underneath the sink, back behind the plumbing. They hold it up to the bare light-bulb hanging by a frayed electrical cord in the middle of their rubble-filled hovel, and they rejoice. The end.
I think it is curious the way these shortcuts develop, so that the utterance of the words Another Potato says, "OK, OK, it can have subtitles, but at least get one with a happy ending," or the words The Last Potato pretty much sum up all past conversations about why we shouldn't rent Life is Beautiful.