i'm going to have to read your other responses on this one (haven't yet) but i'm surprised that you felt the need to write an entire apology in another post.
i have one of those rowdy, rambunctious kids, and i didn't take offense lol.
but i do want to say that in this case, i'd leave it alone. let her know that you still expect her to behave regardless of what M is doing. hold HER accountable for her actions. she may decide that M isn't that great of a friend. it's all a process...we teach them as we go along. good luck.
-also, as Dawn says, make friends with her teacher. if they need separated, great. you sound like me. i was so quiet and well behaved in school, the first little infractions from my lively, energetic, silly little boy mortified me. but make friends with the teacher. she can be your best friend and ally, or your biggest enemy. you DON'T want that. she's there, she has to deal with them. as someone else also said, you can't discipline such a small child, hours later after you get home. it's really on her to deal with.