Nathan would have pointed out that she could take comfort in the fact that the girls were fake but she didn't know that (even if she had a suspicion) so the comfort couldn't come for that particular thing.

Even if the girl had been real, he probably wouldn't have been sweet to her because that sort of thing seemed to come out in special situations like the ones with her.

There were parts of her that Nathan especially liked, parts he liked to kiss and pay attention to more than others. One of those places happened to be her neck and which is why he had two fingers running up and down the smooth skin on the side of her neck while he kept kissing her.