rant/custody situation

So long story short I have a 7(almost 8) yr old step son, I've raised him since he was 2.. potty trained, abcs, writing, school ALL of that. His bio mom hasn't seen him since Mother's Day 2012; from that day until last October 2015 she has not made any contact with him nor tried - no calls no text not even to say hey how is he doing. In 2014 my husband took her to court to get full custody , she didn't show and he was granted it. So in October of last yr she sends me a message on Facebook stating that I'm not his mother I need to stop acting like it and trying to push her out of the picture she's his mother and she deserves to see him. I explained to her, as I did many times when my husband and I got together that I would never ever try to replace her; and to this day I haven't - I just do things for my stepson that a MOTHER should do. I told her I would talk to my husband and have him get back in touch with her bc it's ultimately his decision, not mine as to whether she sees him or not. He never called her back bc she has made no effort whatsoever other than this one attempt.. we haven't heart anything since until yesterday