I guess. The walkthrough implies not meeting Bella if the rob option was picked costs Love points with Bella. Is it the same, if you don't have the option ? From what I recall, the outcome was the same except that Bella delivered another line when she kicked me in the balls.
If you don't get to choose between staying at home and go to Mario you won't get Bella+2 and Dark+2, but you also won't get huge minus in love points, which prevents you from getting points with Bella and Amber in chapter 3.
So if you wanna stay with Nami better not say that you will meet Bella at night. Cause if you will deceive her you'll lost 6 love points, 2 RP with Amber, and one trigger (though you will have 2 more RP ponts with Bella if you deceived her, it's funny)
But thing is, game still reacts like you said to Bella that you meet her at night but didn't show up.