I am honestly concerned about the mental stability of this woman. She has no boundaries. Your boyfriend isn't setting healthy boundaries. His mother isn't setting healthy boundaries. Your best friend isn't even setting healthy boundaries! Its going to be next to impossible for YOU to set healthy boundaries when everyone else in your life is welcoming her with open arms. Sadly, you can't control their behavior. I hope you can work out the craziness, but at the end of the day, you can only change your behavior. If they refuse to change, your only option is to accept this woman (and her craziness) or to move on. Good luck!