Just suggesting. Even in military parade formations the phenomenon is uncommon. I did not see any other suggestions for her fainting and afterwards she appeared all right.
Hot stage lights can cause a person to faint from overheating. I was an MC on a stage in high school and was on my way down but a teacher in the wings caught me. I didn’t actually pass out but felt very light headed just before I looked at him. He said he saw a bit of panic and my eyes roll and he came out just as I was going down. All I could remember was that I was very hot.