Clearly, she hasn't figured out that the world doesn't revolve around her.
Time to call her out on her shitty friend habits. Sometimes we fall asleep or get caught up in work or we forget an assignment and need to finish. But responsible people set alarms, do work when it's given, and value time with a friend more than time spent watching 14 hours of re-runs.
I'd simply tell her it feels as though she doesn't make an effort to be your friend and that you don't want to deal with the mental stress anymore. If she cancels on you again, perhaps her friendship isn't worth it.
If she cares about your friendship, she will pull through. If she cares more about herself, she will fail you.