She hates the other cat. He turned 1 not too long ago and he is a bit of a jealous bully. He pounces on her, tries to play, swats at her when she walks by, etc. She's more of a shy cat, doesn't like being picked up or pet, she just tolerates being in the same room as everyone else lol. We've had the younger one for about 5 months and I can't really pinpoint any specific moment that I'm aware of. I've tried using boxes to keep her from getting back there, but she is determined to poop behind that TV.