I don't know about Bella, but the scene with Nami didn't strike me as sexualized. By this point in the game, it's quite clear that Nami is perfectly comfortable being half-naked around the MC. She wiggles her tiddes in front of him without any sexual connotation. Well, maybe she's teasing him a little, but that's not something serious. It's like relaxing in a jacuzzi with Zara and Vanessa. Daring talks, naked bodies, but no action. When Nami makes a move you can't miss it, like in the ending of the jacuzzi scene, when the MC had to literally push her away to keep the poor wormy's virginity
The scene when Nami finds out about Noji and Nick shows her insecurities and fear of being abandoned, as it was with Summer, when Nami's best friend almost stole both her best friend and beloved roommate from her. I see in this scene that she is facing her biggest fear of being abandoned by the people she trusts and loves the most. And while I agree that she was a bit overdramatic, it was unfair for the MC to point this out. It's like if Amber would tell him that he's overreacting with his panic attacks. And her gesture when he wraps his arm around her breast and she pulls his hand closer, I think it's her unconscious attempt to keep him close and don't let him run away with the blondie bitch, rather than something sexual