But Erica can't control Ruffo, maybe you're missing something.
Here is how I think Erica can gain leverage over Ruffo:
Ruffo's self-image, the story he tells himself, is that he is improving to become a nice guy. (If this is true doesn't matter, it’s the story he tells Juliet.) Juliet believes this story and expressed this to Erica. Juliet sees Erica as competition but also a friend. She tells Erica (scene 2017), “…you’re a good person “. So there is leverage potentially through Juliet.
Erica can play referee to Ruffo’s behavior. She can offer Ruffo what he wants most, being seen as better, but only if he acts better with Erica as witness and referee and importantly when under pressure.
Kaori can then use soft power “If you want to spend time together, then learn restraint.” She can also use subtle cues in public as to Ruffo’s behavior. She can praise him when he’s good and ignore or be annoyed when he isn’t. The under pressure part is important for this to be real.
This fits her pattern so far. And this creates triangulation tension. Erica’s intimacy with Ruffo is not just affair heat, it becomes loaded with self-improvement and harm reduction to others.
The three pressures in this are Erica’s rationalization, Juliet's trust, and Ruffo’s fear that Erica can define his story to Juliet and others.
Erica might be able to control Ruffo through her, control of access to herself, her influence on Juliet’s view of Ruffo, and Erica’s position as public witness.
In a scene, this could play out as Erica meeting Juliet for lunch, and discussing a recent event with Ruffo. Erica could carefully but honestly tell Juliet what she saw. Ruffo would then hear about and come to Erica not because he cares about the facts, but he cares about the narrative.
Or in a scene, Ruffo is acting inappropriately and Erica could say “After you acted like that, I don’t think I can look Juliet in the eye again.” If Ruffo bullies Ed, Erica would say “if you treat my family that way, then you’ll treat me that way too.”
If this becomes puppeteering then it doesn’t work. Erica can’t directly tell Ruffo what to do to get something.