“Best Friend”?

I have a “best friend” that I have had since high school and we’re both 22 now. I haven’t seen her in four years because both of us have been so busy with college and working. But between those years, we would make plans for lunch, dinner, shopping trips, and other get togethers for us to spend time with one another but she ALWAYS cancels on me, especially at the last minute. She has cancelled on me repeatedly that I have lost count. Should I not see her as my friend anymore or am I being too sensitive about it? I would love to have other people’s opinions on the matter. Thanks in advance!