based on what you've said about your girlfriend's tastes, I would choose the bella! both are beautiful, but i think the bella represents all the understated, yet upscale preferences your GF has. The bella is so perfect!!!
I like the classic the best because of the detail on the sides BUT the way you talk about your GF it sounds like she doesn't like something to be showy, and likes understated beauty and that's what I think the Bella is. With the Bella at first glance it looks simple but when you look at it closer it has a lot of detail.