----------------------------------------
Nishino reaction of Kozue was normal, all girls would be jealous if their boyfriend/date is chatting w/ another girl.
I think this is the breaking point for her, after realizing her surrounding is couples. She wanted to be Manaka girlfriend again. Things got worst when Manaka caught up and held her hand, which she ran away, because she doesn't have the right to hold his hand as a girlfriend. Since their reunion up till now, she hasn't directly said she love him, but hint subtle messages to him that she still cares for him. My thoughts is that she wanted him to confess again, but he was so dense and insecure about his relationship w/ Nishino up till now (currently friends). Then their were the other girls distracting him with from committing, and vice versa with Nishino to the other girls. I notice few chapters before this, Manaka starting to put some thought about his relationship w/ all the girls and how to end it w/o hurting anyone.
Nishino owned by couples.
http://i2.mangareader.net/ichigo-100/141/ichigo-100-385599.jpg