As a Van Tassel Junior, she's probably very well acquainted with my kids.
Gracy probably flirts and pursues her tirelessly, because well. Pretty face. Same house. Makes sense to him.
I have a feeling Nat does not like Emilie. Being that Em is a rich girl from Manhattan with a bad history in the local area. I assume she doesn't get along with people who can read people very well-- which Em probably will, and can if it's cool. They're both characters that seem to like to hide behind walls (well, both my kids are) so things could get complicated.