Jurupa is right.
You probably need to flirt a lil bit more; try and build a flirty connection

That'll get you where you want to be. Your conversations were very original, not that they were too average but there should've been a "hard-to-get/I-wouldn't-care" flavor, you know what I mean?
Girls are usually flaky when they're
not interested OR
when they're interested in you and are insecure - shit tests and shit games (who've had bitter relationships in the past)
The only way to deal with such girls is to be point-blank and specific when you say something ("Ok, I'll meet you at 8 sharp") It's like saying "I'll be there at 8 and I'd want to see you there by then or I'd go away" Well something like that.. Get it?
Some girls would still tend to act flaky no matter what... And that's when you should get out of the box and go date someone else.