Uh, based on what I've seen of her, Mika Nakashima isn't really the smiling type. That picture with her and Ayu doesn't really prove anything.
Hah! The Kumi and Ayu pics and captions are hilarious
But it's kind of hard to talk to someone two seats away. And Kumi looked like she was listening in on Max's conversation. She wasn't really looking at Ayu.
At least Ayu said "Hi". That's enough. Even I don't say "Hi" all the time.