Not auto tune, her vocals were echoed which is the effect they use on the actual track. It's impossible to sing the song otherwise tbh, the chorus "And i feeeeeeeeaeaeeeeel" has too many effects on the track that you simply can't replicate live.
There is delay but there is definitely some pitch correction as well. I use auto-tune all the time and you can tell by the way her vocal slides correct to notes, and sometimes when she's slightly off it corrects it to the wrong note. It's most noticeable at 2:57. She used it on this performance too, except with less delay.
(unless it's you kworb, then you're forgivenm but i think it's not you)
