I think Emily is messing with Sam - I don't think Emily is asexual, though. The fact that she thinks about butts being cute, has had at least one boyfriend, and talked with Marten and Claire about kissing seems an indicator that she has spent time thinking about sexual topics. I was under the impression Asexual meant you weren't interested in sexual activity, so that doesn't seem to fit. And yes, I suppose having a boyfriend and kissing don't necessarily mean sex is involved, but thinking about cute butts would likely lead to a sexual thought or two. Overall, Emily seems like she'd have more of a problem finding someone who doesn't mind her odd ways of thinking than not being interested in sex. Maybe Clinton?
Aside from all that, she makes me think of Luna Lovegood from Harry Potter in some ways.