Potential MOH acting like my MOTHER?

I've been meaning to ask a cousin to be my Matron of Honor, but she's suddenly been acting like my my mom. She found my Facebook page that had a note about my physical health on it,. She replied that I'm just attention seeking, blah blah.....instead of coming to me. I eventually took the note down, but I'm seriously rethinking asking her to be in my wedding, especailly at such a high honor....