As much as I love the image itself, I'm really sick of the queerbaiting with these two. Don't wag the bone in front of my face if you're not going to throw it.
Of course, KyoAni is welcome to shove my words back into my mouth and pull a KorrAsami. I would gladly shut up.
I'm pretty certain the only one who refers to her as just "Nico" is Eli.
e: shit, I have Maki referring to her that way, so there's no consistency. Anyways, just "Nico" + casual language (doesn't come across in the TL) = Eli for sure.