I think you're in the minority concerning assessment of her beauty. Then if you're looking for an "interesting story," I suggest "The Emperor's New Clothes." The media does this all the time. They just did it with Sarah Jessica Parker, who is flat-out horsey, but the media loves her, so she is a sex symbol. Diana wasn't ugly. She just wasn't pretty either. And she was a princess. Grace Kelly was pretty.
Diana was every bit as pretty as Grace Kelly. Diana's problem was that she was neurotic, moody, manipulative, ruled by her emotions, and lacking common sense. If she had not died, I believe that too much more of Dodi and the al-Fayeds, successor playboys, chasing after other womens' husbands, and even the Chuck-bashing would have caused the Brits to turn on her eventually. She was getting to be a bit too publically tawdry.