In horror movie Annabelle Comes Home (2019), Daniela meets Judy, who is feeding chickens:
Judy: So, are you scared yet?
Daniela: Scared? What? No.
Judy: Who says they're scared?
Daniela: Kids in my class. Anthony Rios started it.
What does "they" refer to?
Who says they're scared?
This is a common type of question / expression.
It's just a way of saying "Who would say that about themselves?"
In other words, it's not something that one would admit normally and so the asker is questioning who would admit to that.
