Why doesn't anyone in the studio hear that one shrill soprano?

I love choral music, not only operatic choruses and church music but especially choral renditions of Christmas music. I’m listening to some right now. And what I want to know is: why is there nearly always that one shrill soprano, singing a little sharp, loud and bright as a crystal?

How did she get into all the choirs? over decades?

And why didn’t anybody hear her in time to excuse her from the recording session?

I’ve thrown away entire Christmas albums because of her.

Sometimes (though rarely) I even hear her in the Mormon Tab. And sometimes she even sneaks into an all-men’s group like Chanticleer, disguised as a high tenor.

I don’t fault her enthusiasm or begrudge her the joy of singing. But why is she on the recording, stinging the air with that biting sharpness at the top of the scale? Don’t they hear her?