"I could totally seduce you right now. No problem." She tilts her head thoughtfully. "Well, if I wanted to anyway."

He's not a thirteen year old girl, so he doesn't think he can't live without her or anything as melodramatic as that - but he's come to realize that maybe he doesn't like his life as much without her in it. Post-S5

There's been something more than friendship between them since nearly the beginning – even when they weren't able to recognize it, even when they didn't want to recognize it.

Or maybe it's that she has changed and she isn't quite as willing to fall back into the role of the group's sweet, innocent little baby.