She's always been exceptional. Just look at her stats. She had a 46-3 record on the USTA kids circuit when she was 9. She wasn't gene doping then - if she even is now.
From wiki "Ranked world no. 304, she upset world no. 7 Mary Pierce and world no. 4 Monica Seles, recording her first career wins over top 10 players and becoming the lowest-ranked player in the open era to defeat two top 10 opponents in one tournament."
She was 16 at the time. That's simply remarkable.