This movie, and it's plot, will make more sense if you do a google search or equivalent on the theory or myth of a doppleganger. I understood it better after I did, and enjoyed this movie!
shareI think it's impossible, without facial surgery, to not know the difference between your husband of 10 years and "Roberto." There are too many items on the body that are not identical to your "original." Even celebrity look a likes don't look exactly like the original. So, how did she miss something like his junk size, his earlobes, nipples, body odor, hair color, fingers, eye brows or highlights of the eyes......?
Now, it was implied that they did not enjoy sex and that he was usually asleep when she entered the bed. What, you never showered with him? Never explored each other's bodies? I would certainly know the difference between my girlfriends, wives, husbands or who ever I had a long term relationship with. I would definitely know her body and her personal scent. I would know every mole on that body of his wife.
This is late but I agree. It is not just the way a person looks. Actually that is a minor indicator to me. And if it about looks it is about stuff you mentioned. Gee something looks different about Joe, I know what it is that eyebrow. His moves different when he talks. Why isn't he laughing at my bad jokes? Wait he laughs differently.
I can tell who is in the room with my back turned away. Voices are different and scents and it has nothing to do with perfume. People have different scents to their bodies. Their sweat smells different and their hair, body scent differs. I find it unbelievable she did not know who her husband was. I know who someone is after knowing them a few days.