@Ryll - Yozora may not be fully aware that she is in love with Kodaka, and that is the cause for all of her attempts to look boyish in order to rekindle their old friendship, but everything else she does shows that she likes him romantically. Just the fact that she is possessive and gets jealous is proof of that. Friends don't do that.

Also, Yozora was indeed upset that her plan for Yukimura backfired on her. But why would she be upset at all? If she didn't care about Yukimura's gender and its effect and Kodaka, she would not be upset at all. I just rechecked that scene, and now I'm sure Yozora is pissed because a very powerful (cute, considerate, devoted) rival appeared, one that she never even minded when she thought of her as a guy. Yozora's lines clearly showed this.