Weddingbee boards

I need some serious adivce.  I think I have to fire/demote my MOH.  I don't want to end the friendship, at the same time, I am very upset with her.  We have only been friends a couple of years, and she was not my first choice of MOH, but she and I were hanging out a lot and she was being an incredible friend to me, and kept pestering me about picking a MOH and how it would make her life so much better, so I picked her.  Months later, she's started behaving like a 13 yr old girl, stressing me out about boy problems, and stupid nonsense, and seeming to forget all about her MOH duties, the first one being DON'T STRESS THE BRIDE OUT!  My fiance and I have both given her advice and she doesn't take any of it, but then wants to complain about how things aren't working out all the time.  She ruined wedding dress shopping with my mom and FMIL bc she was all upset about a boy she had just met and hung out with twice, was bitter and stand-offish during lunch, and rude when my mom asked if she could run into the store to grab a couple things while we were driving around. She ruined shopping for BM dresses with a couple of the other girls bc all she wanted to do was talk about her and her problems and how she was planning all of these things that she actually hasn't, and kept cutting off the other girls while they were talking to me.  None of the other girls like her.  She has embarrassed me in front of several friends on multiple occasions, talking about inappropriate things she has done with guys.  I am terrifired she will get up to make her toast and really say something terrible (I could be wrong, it could be amazing, but her track record points to her getting drunk and making a fool of herself and me). I could go on and on and on about the things she has done to embarrass me or make me not really trust her anymore.  I don't want to make her an enemy, but I think this friendship has seen its time.  I need help, what whould you do???