If you watch the whole Lionel performance, she was struggling to reach some notes. She sang fine, but at some notes you could see some struggles to push higher.
Also she's capable of usually performing with bronchitis, just that this time she had a risk of her of her blood vessel in her neck BURSTING which could PERMANENTLY damage her voice. Although nowaday you can bounce back, it happened to Adele and she had to stop singing for several months, and sometimes you lose your voice permanently like Julie Andrews.
I'm disappointed she didn't perform, but **** happens. Also I was worried something worse happened cause Jared made it seen like some catastrophic had happened so I was honestly relieved when it was "just" bronchitis.
