I'm going to share with you guys my bullet-proof technique on flaky girls. Without further ado, here it is :
( after you set a date and she cancels at the last minute )
Hey - I thought you are interesting and fun to be around. I really want to get to know each other a little better. If not, then let's just be friends.
Success rate : an honest to God 10 out of 10 ( as of Sept. 2010, never had to use it since then, but never say never ).
The reason behind this is that it throws her off completely. Chances are very high that she has never heard such a thing from a guy before and therefore she will most likely respond with "No, I really want to get to know you better and I think you're interesting too." and some other details and in some cases a re-schedule ( one time, a HB invited me over to her place because of this message ).
This is Push Pull at it's best.