I noticed Bonnie clutching her neck as if she had been triggered and instinctively knew something was about to happen, but I didn't think that had anything to do with her parents. We didn't see her parents, not even in flashbacks, until the second season. We only heard that Abigail liked spending time with Bonnie's mother, but nothing about abuse. I thought Madeline lied to avoid scrutiny from potentially unsympathetic law enforcement. I could be wrong but I don't think Madeline knew anything about Bonnie's background at that point. Did I miss some background about Bonnie's parents? I noticed they've joined this season and there's definitely something up with her mother.