I agree with Nikki. You chose this girl to be in your wedding, and therefore chose to have her in the midst of all your friends and family for a whole week. You know how she is and who she is, and if she is 27 most likely she is not going to be changing. Your guests can make their own decision how they handle it, ignore it, stay away from it, but telling your BM to not be herself, basically is what your wanting to do, would probably only hurt things not resolve things