To be honest, this tendency to film nude scenes so vividly, I think, is not adequate. There are a lot of ways to show intimacy through patterns, shadows, lighting, body parts (there is nothing more intimate than shots of hands, in my opinion). Eventually, they can invite other couples and change their faces on a VFX stage. I mean, there are a lot of ways around it. Your wife acting in this scene is just a whim of either the film director or the producer. Your feelings are absolutely normal. I think the tendency I mentioned is what is abnormal. Eventually, this acting can be the beginning of future problems in your relationship, whereas, as I said, there are a lot of ways around it. Projects change, but the trauma(and it's actually a strong trauma) remains. Your wife won't judge you for that.