Turning the Tables
Right now, your best bet is to just not worry about it. If she doesn't respond today, then send her the following message tomorrow.
"Hey, I figured that someone of your attractiveness would be the type to quickly forget someone. But you know, looks can be deceiving, so I decided to give you the benefit of the doubt. Have a nice day."
This comes from a reading by Derek Rake. As he explains in there, a woman is always prepared to give a speech in this category. However, she is almost never ready to receive it. This is also effective because it basically challenges her to prove to you that you are wrong.
What she'll probably end up doing is send you a text message back apologizing for not getting back to you and that she is actually a nice person. At this point, you could say something like:
"So you're not usually like this?"
This is the ultimate bitch shield destroyer. This shows that you are not willing to stand up to her garbage, and that you will abandon her quickly if she gives you any more of it. It is basically a powerful show of hard will and manliness.
Finally, she will probably text back saying that no she isn't. At this point, you can actually set up a date, believe it or not. You should also include a little bait and lure for her to come too. Something like this:
"Well, if you go to [coffee shop] at [time] and buy me a coffee, I might forgive you, and I might also tell you about [awesome, potentially made up story about you]."
I personally already have a crazy near-death experience of mine involving a dog, a semi, and a cheeseburger. The point of the crazy story is to spark her curiosity and interest. With my story, the outlying details just sound so ridiculous, you absolutely HAVE to figure out more.
Do all of this right, and it will be hook, line, and sinker for you.
"There is no better than adversity. Every defeat, every heartbreak, every loss, contains its own seed, its own lesson on how to improve your performance the next time." - Malcolm X