Years ago a friend of mine was in a similar situation. Although it was legal to keep hens in her area, she checked with the surrounding neighbors to make sure no one would take issue. No one did. Months later, one of them filed a complaint with the health department (without ever speaking to her) that her coop was filthy and was causing rodent and odor problems. An inspector came out to find my friend's coop, run and yard immaculate. She had great rodent proof feeders and a deal with an urban farmer to take away soiled bedding so that it never piled up on the property. He gave her the blessing to carry on and that neighbor was cheesed! I know she is only complaining about the noise, but I would make sure you have every single base covered in case she decides to try to get even more petty.