Trouble in Friendship Paradise

I have a MOH who I feel like I have fallen out of step with. I feel as though she does not put me first in any situation. Here are some examples:

1. When I had my engagement party I sent out the invitation weeks before the date with the time and other information, and she offered up she would help me set up for the party. We get to the day before and she tells me that she would be able to get to my house at a certain time (which would have been hours after the party started) because she had an eye doctor appointment. Then realizes she will actually be late and can't help.
2. For my birthday this year she suggested doing something to celebrate and we were going to go to lunch and walk around a small town. We planned it a whole month in advance. She texts to ask to cancel a week in advance so that on the day we planned to hang out, she could instead, have her new boyfriend meet her family and instead wanted us to reschedule. At this point I told her it was hurtful that she assumes that I am always available to reschedule and that I feel like she does this all of the time to me.
3. Most recently, I planned a trip to NYC with a few other friends including her. She paid for a ticket and 2 days before she bails with a weird excuse about another friend of hers father on his deathbed and needing to be around incase something happens.

These are just the most recent examples that I can recall, there are definitely a bunch of other times she has bailed with plans that we have made and now I feel like I've made a mistake asking her to be my MOH.

I understand things happen, and in certain situations it is totally okay to reschedule, but it has just happened too many times.