@ippn1,
You're both playing games.
Grow up and grow a pair. Passive-aggressively not answering because you've decided this woman is flaky is your own flakiness coming out. If you're not going to provide an answer to a reasonable question, then why are you hanging around with her, and why are you even thinking it's going to progress? People do, you know, have lives outside of dating. Someone being busy or forgetful or having other plans, that does happen. If it's happened exactly one time, it's hardly what anyone would call a trend.
By the way, if you were looking to blow it with this girl and tank any possibility of a relationship, congratulations, you have done the right thing.