I would text her saying: "Guess what?!? I just saw your twin!! Seriously, this girl looked JUST like you!! That is, unless your one of those women that like to stalk me!! I know Im studly and all but"
It's playful, intriguing, a dhv, fun, cocky funny, puts her on the spot, and isn't wussy. You have to respark those emotions and attraction she initially felt for you. If you keep pouring on the cocky funny humor, she will see your not just like every other guy and will likely ask to make plans again.
This time, set it up in a way that she will be meeting up with you while your already doing something. For example, you could say, "I will be at Starbucks doing some work, if you want to meet up with me great, if not that's fine too."
If you frame the situation where you don't really care either way, whether she shows up or not, you don't care, you'll be doing your own thing. Trust me, it's worked for me when setting up first dates with a woman I suspect may be flakey,