 The woman who burst onto the scene three years ago only to see her Olympic trip squelched by a positive test for marijuana has been leaning on the mantra, I'm not back, I'm better, ever since winning the U.S. and world titles last year. She has yet to tell the full story, which includes bouts with depression and the death of her mother. Whether she stays in the spotlight depends a lot on how she fares in the 100-meter final, which is set for August 3rd in Paris.