CAD1223, I was waiting for someone else to answer, and hope they still will, because smart casual means different things to different people. I think the dress you described would be fine for Portofinos. As I understand it people dress up a bit more at Portofinos than in the dining room. I'm only speaking from what I've heard because I haven't yet gone to Portofinos (and that's why I hope someone else answers). Your friend may also be comfortable in what she plans to wear if it's a dressy blouse (not like a t-shirt top). It depends what each of you is comfortable wearing. You could also ask the matre-d at Portofinos. Maybe you would want to switch dresses and wear the cocktail dress to Portofinos and the other dress to the formal night at the dining room.
Cruise guro Raoul Fiebig wrote the following about dress code at Protofinos and Chops. "no - formal clothes are not required. "Smart casual" is fine, although if you would like to dress up, that's fine, as well."
Have a great trip and, by the way, welcome to cruise-chat.