She described that night as her first real concert (since the only one prior was at an intimate venue and had a shorter set-list), so she was indeed nervous. These are some of pop music's hardest songs and it was sort of her first showcase of a bunch of them on TV and to be put on an album. In an interview, she feared that she wouldn't be able to access her whistle register multiple times due to the set-list, so there was that pressure. She did Emotions twice because the first time she had many pitchy, unsupported notes. I don't know what the second performance of If It's Over was for because the first performance was actually good. Plus she has a life-long struggle with a vocal disorder that affected her consistency (for another reason why she could be nervous).