I suggest simply parenting all of the children when u are with your friend. That is what I do and it works. I have a girlfriends whose kids are unruly, well actually horrible. I simply handle everything and now her kids listen to me and we have no trouble because they understand my rules. If your friend does not want you to parent her children, then I guess the friendship would be over for me. I refuse to be around unruly children, when all they need is alittle guidance. All of my friends expect me to do this, so it works out. I never hit or ridicule I just get the kids distracted from their behavior and onto another task.