I agree with Ziki. It sounds like you had like a 5 minute number close. No rapport, and just enough comfort for her to give you her number. Happens all the time. She wakes up the next day groggy headed and barely remembers you... It happens. Understand people have busy lives and my not always get back to you in a timely fashion.
You have done enough. Don't extend yourself any further right now. Especially if all this went down on Friday, because you are showing too much interest. When you see your ex coworker out just shoot the shit with her. Don't worry bout this girl, cause she sounds like a flake.
Next time when you #close create a bond. I have a unique handshake I do with girls so that she has something to really remember me by. Its something I do to build a connection. Another thing is to set up a time to meet up again right on the spot. This way she already has an idea of something to do next time she sees you...
Example....
Quote:
This is awesome we have met tonight! Since we are BFF's now, you need to meet me up at the mall for a smoothie and help me pick out some new boots/clothes/what-ev. I'll give you a shout this weekend and let you know what time to meet me.
If she is interested she will let you know when she is available... It just helps to stay memorable and build a connection.
CK