Ok, this one I know well due to many years of being single and dating (tho married now). If someone does't follow up and gives mixed signals, it's because they're not that into you. Maybe they wanted to be save themselves the discomfort of letting you up front and just blew you off instead - that's the easy way out. Sometimes the prospect will do some things that make you think they're interested but they are inconsistent. That means that they're not that interested in you or might just be sending enough signals to have you around if/when they want and that's it.
Bottom line is this: you can NEVER believe what a prospect says early on. Some people have practiced their game face so well you can't tell it from true sincerity. Just wait and watch their actions, and then you will know. If she doesn't call, she's not (that) into you.
It's nothing to take personally - every two people no matter how worthy are not necessarily a good match for each other! Good luck :)