I think Acht might be the true villain of Side Order, she showed up at a suspiciously convenient time when Agent 8 and Pearl didn't what to do. Then you have the fact that she knows Marina from "way back", even though Marina didn't say anything about knowing anyone who was lost to Sanitization.
To me, that points Acht toward the idea that she's the true villain, bent on Sanitizing everyone in the world by luring others into her trap. Starting with famous figures first, then using them to convince everyone else to be Sanitized.