Rule of professionalism #4:
When your interviewee shows up at the postponed time, apologize again for inconveniencing her.

Rule of professionalism #5:
End each interview with some sort of closure so that the interviewee knows what to expect next. Some examples: "Thank you for your time. I will contact you via email within the next week." "Thank you for your time. We are interested in having you on board, so please let us know within (name the amount of time)." Or some facsimile.

Basic rule of thumb:
Become a bishop. Then you can make people do whatever you want and live like nobody is as important as you are.