I could be way off here, but...From your description it doesn't sound like she is killing and eating them or killing for sport. It may be her own maternal instincts (sexual maturity/breeding age) from the incessant cheeping. I had pyrs for 20+ years, though not around livestock. I had a 3 yr old female that found a box with a litter of day old kittens that someone dumped. I took them in to care for them. She would panic when they cried and kept stealing them, walking around with them in her mouth looking for a safe place to hide them like they were her babies. She wasn't trying to kill them, but you know, tiny little things are particularly delicate. Just a thought.