8, the fact that she is having an A is not "fine" but it's something you choose to live with for the time being. Personally, I would not bother with the necklace thing. Think it through, you tell her not to wear it, she likes it and wears it anyway. Are you going to end the M? Probably not, but you are putting yourself in a position where you must back up your request with action. I wouldn't go there unless you are absolutely sure you will follow through. You've told her your feelings about flaunting OM and, with this exception, she has respected them. Count it as a victory and move on. By making the necklace the focus you are making OM the focus also. I'd let it go. Just my 2 cents.