I am so sorry for your less than stellar duties as MOH. You were very gracious not to pummel her before her bridezilla event/wedding! I APPLAUD you for speaking up for MOH's and the bridal party. I honestly hear a lot of complaining from a lot of brides about what they don't do, or aren't doing for the brides, but rarely do we get to hear the other side of them being mistreated, unappreciated, and seriously abused, as you yourself experienced! I've heard of some serious demands, but cleaning up after them? use the money you saved on the bridal party's gifts, and hire someone, cheapos! Sorry.
In the long run, if you show her all the appreciation, and gratitude you were never given, it will hopefully show what a bigger person you are, and make her realize her mistakes (if she's a regular human being, and seeing that she must have had some good qualities to be your MOH, i'm sure she's got some civility deep down!) That way, you don't need to get revenge, she will suffer in the way of guilt! Best of luck, sincerely, and I hope everything goes alright! (if it hasn't already, i see this post is a little older!)
I didn't speak to a best friend after being her MOH for reasons very similar, and wish friendship didn't have to break over something that should be a wonderful experience!