[Are there detectives in The Godfather? If there are, they probably die or get tortured or something. Naoto doesn't know, either, so she can't correct her even she wanted to. And she doesn't want to, because Rise's cheerfulness and enthusiasm has a way of discouraging Naoto from being a grumpy pedant.]

I believe "an offer you can't refuse" is spoken along the lines of a threat.

[Orrrrrr not. Except Naoto says it with a smile, to show that she's not grumpy and still likes the idea.] So, er… that dark blue, maybe? Or straight black? [She should probably be more decisive, but Rise is going to be the one that has to look at her all night.]