It's obvious she's singing live. Just compare her last three performances of this track & you'll easily notice that the vocals vary each time eliminating the possibility of a pre-recorded track for her performances.
She's improved so much and I'm so happy to see how far she's come and the success she's been seeing, so far, this era.
Watching this performance compared to every other performance she gave earlier in her career (let's not relieve that performance of LYLALS at the TCAs) is like one huge miracle. Her vocals/stage presence has improved alot and this SLAYEDT. And now the single is Number 2 on iTunes, get your well deserved recognition finally selena
One thing I've always wondered: Why do so many pop stars hire fake backup singers for their TV performances? Am I really supposed to be believe her backup singer sounds exactly like Charli XCX? It's just silly.