I really think that there was some kind of massive misunderstanding between the two of you about what a MOH does way back when this first came up. First, I've read every single one of your posts and I still can't figure out why you would need to move your family to become her MOH. And, I realize that this was probably (I hope) hyperbole, but, what do you think the MOH does that you couldn't do it on the wedding weekend? My MOH lived 9 hours away. She never came to see me once before the wedding. When I was her MOH, I went to the wedding town on Wednesday or Thursday for the Saturday wedding.
Yes, if the BTB expected you to plan and attend a whole bunch of pre-wedding activities, then you couldn't do that. But is that what she expected? And, if she did expect that, didn't she expect it from her other BMs? Which means if you can't do the MOH job, you can't do the BM job.
I've been a BM 6 or 7 times. In every single one of those weddings, the "work" done by the MOH and BMs was equal with some local BMs picking up a bit more on things like hostessing. I've hosted probably 5 or 6 stagettes and at least 1 shower and I wasn't the MOH for any of them. I wasn't even a bridesmaid for one or two. The girls who hosted my stagette weren't my BMs either.
I think that if I were your friend, and I'd called my preferred MOH and asked her if she'd be the MOH and she started offering up a bunch of excuses about why she couldn't do it, I'd assume she didn't want to do it. And, I'd completely understand that. God, I've done the BM thing so many times that when one of my newly engaged friends called me and asked me to emcee her wedding, I literally did a happy dance while singing, "Sarah didn't ask me to be a bridesmaid! Sarah didn't ask me to be a bridesmaid!"
So, if later on, that same friend had told me she wanted to be a BM, I'd be confused. Because if she can't or won't or doesn't want to do the "work" of being MOH, I'd assume she couldn't or wouldn't or didn't want to do the work of being a BM. And a conversation would probably happen much like the one you had.
So, all that said, if she's a bad friend, she's a bad friend. And, if you feel that her overall behaviour over the course of the past 20 years of on-again, off-again friendship has not been good and that you're better off without her, then yes, you should disengage from this friendship. But I don't think you should blame it on this incident.