How to approach a girl when she forgets to talk to you?

So there is this girl i like but twice in the past 5 days she says she has to do something and will text me in like 15 minutes. She never does text back. Is she forgetting? How can text her when she doesn't respond?How to approach a girl when she forgets to talk to you?
Say this: You little forgetful basterd. Why didn't you text? (but playfully)





Girls will apologize because they won't believe themselves as that. But playfully, or else you're a jerk to 'em.