It depends on the angle you're looking at. When your eyes are looking straight ahead and forward....or upward...the nose and cheeks should not be visible at all, normally. When you angle the eyes look a bit downward, however, then you will see an out of focus nose and perhaps some indication of the cheeks too (depending on how round your cheeks are, I suppose, because I barely can see any part of mine.). When you look to the side you will see a sort of transparent image of one side of your nose, and if you close one eye, then it's not transparent anymore, it's just out of focus.

Perhaps your girlfriend tends to move her whole head up, down, or to the side when looking that way, instead of simply angling her eyes that way...? If so, then she would not tend to see the nose or cheeks.

Get her to look, but not move her head at all when she looks, and then see.