Her official stats are 5'4 108lbs, which is 18.5 bmi. Exactly. So may be coincidental, may be fake to stop media gossip. That's low, but not necessarily bad. Her arms look thin, but there's always muscle showing, and her legs and everything else that's visible look fine. I'd guess she works out and has low body fat. She also has a weird face that's making her look odd.