Responses
I think you misunderstood. It's not that he stared at her body. He was to pretend to be her, so he needed her dress, which at that time, she was wearing. So naturally, he had to take it off of her and dress her in her nightgown (as seen in the start of the chapter). So technically, he HAD seen her body, but it was out of necessity. He's not a pervert, he was just teasing her.
Are we all just going to skip over the part where he says he looked at her body when she was UNCONSCIOUS. Umm hello??? I hate it when people just excuse awful behavior just because they will end up together.