I don't think she was. There was a certain raw, organic quality to her vocals that indicates no processing or mastering that would have been present in a pre-recorded track. If she was lip syncing, it wasn't obvious. And if you're talking about the backing tracks... duh.
Everything is tracked. 99.9 percent of live performances for tv arent live, even if they sound live. That is why they go into the studio and do a "live" version of their song.