Monster-In-Law

I have a monster-in-law.... 
Two weeks ago she text me & was getting aggressive about me "refusing to have children with her son", not "getting it started" and make accusations that I'm trying to hard to be "prepared" and making my Husband's life miserable. 
(My Husband told me he hasn't ever mentioned us TTC or planning on children, because this is the crap she pulls) 
Now, Her and I have always had tension and conflict, everything I do is never good enough. 
Little does she know, we want to start TTC after the Holiday Season when our lives aren't so hectic and busy.
The problem is that I don't want to tell her we're TTC, because I know that once we become pregnant, she'll tell everyone she was the first to know & kinda, sorta rub it in that she knew before everyone else.... 
Any oppinions? Thoughts?