I mean, unless you're against the existence of cops in general, she's planning to bluff him that she knows what he's up to and let his guilty conscience do the rest. If she knew what he was doing that was illegal, she'd actually call the cops, because that's what you do if there's something illegal happening.Basilisk literally just left the police force because she didn't want to be a part of cops intimidating people.
So instead of threatening to arrest the manager herself, she's threatening to call the cops and have them arrest said manager. Using knowledge and contacts from her days as a police officer to do it. I guess that's better, but it's still not "good".
So it's not 'I'm going to have the police harass you for nothing' is my point.