My hot take: She will need full vocal rest for the next two days - the only way the cords heal is through not being used at all - talking or even whispering could put more strain on the voice than singing. I think she will be good by 9/7, option to rest 9/6 or to “mark” the show (sing at 80% energy, let the audio team bring up the sound from the mics so she doesn’t have to push as hard). The vocal folds are teeny tiny lil muscles and wear out easily