As you can see what you are doing is not working...(or going to work)
You ARE trying to control her...
This really isn't how you do it. You are mistaken and going about this wrong...
You should be telling her you want her out and that YOU DO NOT KNOW HOW YOU FEEL ANYMORE..
"WAW, you can talk to anybody you want to. I am not sure how I feel about you anymore, but I think it best that you find another place to live. You can then talk to anybody you want to on the phone, in person or on FB.. I think that is for the best."
You can't make them stop talking to the other person by trying to be a security guard. It only works when YOU let go and THEY come back to you WANTING to make it work because YOU have let go. It is then that you tell them that you don't trust them and you just are not sure because you don't want to worry about whether they are still in contact with the OM. The WAW THEN tells you they will give you their passwords and anything you want.. This then makes it THEIR idea and is done because they WANT to do it and not because they are forced or cajoled into doing it...
I know you think you are setting some boundaries here, but you ars sadly mistaken and fooling yourself.