Again, this is making no sense.
An athlete passing a test is an indication that they're clean.
Yes an athlete passing a test in an indicator that they are clean, but its not 100% beyond all doubt proof.
I'll give an example, the Bahrainian athlete Rashid Ramzi, was a long suspected doper. He won the 800m/1500 double at the world champs in 2005, then had a couple of off years relatively and didnt win another major champs. He turned up to the Beijing Olympics and wasnt considered to be among the favs, as his form was unknown. But he won the 1500m final. Most observers thought it was a bit fishy. He then passed his drugs test as he had done all the others. The testing at Beijing was the best available at the time.
Come 2009, and testing again had improved. His sample from Beijing was retested and he was found to have been using CERA, an advanced type of EPO. Testing for CERA wasnt available in 2008, but was in 2009. He was stripped of his Olympic title and received a ban.
Basically what I'm saying is, only the stupid and careless get caught. The athletes tend to move onto the latest drugs for which there is no test yet. IMHO the biggest deterrent is the retesting of samples years later when the testers have caught up with the latest drugs. As it stands the testers are always playing catch up, as they cant test for substances they don't know athletes are using yet.
She has passed the test now. But only time will tell