Your friend is EXACTLY how my friend is! I've had all that with the calling as well! I know shes not worth being friends with but for some reason i cant seem to give up on her. Just try not let it bother you, i know its hard but im sure you've got much better friends. In all fairness she could have been busy or just genuinely forgot, but if she is anything like mine she would do it on purpose!
My friend said we would meet up, i hadnt seen her in like a month. So when i heard nothing from her i text her and she said she couldnt be bothered. The thing is she doesnt even know im angry because i always leave stuff like this, im a complete push over and im sick of it!