Olympic 2012

I have been passionately following the Olympic 2012 especially the swimming events. I was amazed to see the 16 year old girl Ye Shiwen from China winning the gold Medal in 400m Medley. I became stunned while I found out the reaction of some of the people. They suspect her performance enhanced by dope! That's strange, when Stephanie Rice improved her personal timing 5 seconds that was a great performance or when the 15-year-old Katie Ledecky from USA wins the 800m making almost a world record , nobody questions her performance. After a lot of hard works and perseverence does the athlete really deserve this?