Twitter went off on Selena's first public performance since getting a kidney transplant earlier this summer. Fans called her a "fraud" and accused her of lip-syncing her new single, "Wolves," since she kept her head down and covered her face for most of it.

But sources close to Bieber's gal tell us that's not true and she only used a backing track on the chorus, which is common during live performances. She also didn't dance because she wanted to sing live. It's also possible the live feed wasn't mixed properly for TV.

As for looking miserable during the performance ... we're told it was all part of the act and that she wasn't sad at all.