Cana might not smell like Gildarts because she was hardly around him, I guess? They have very little resemblance apart from their hair.
As for Silver saying "Natsu...no it can't be" (@noobzilla), this might go together with another theory someone said before on another chapter.
END = Evil Natsu Dragneel?
MAYBE, just MAYBE. Or
END = E______ Natsu Dragneel Something, just it might be possible. Maybe Silver is drawing a connection to that.