Hateful Mother in Law

Ok, so does anyone else have to deal with a hateful Mother in law? My boyfriend and I have been together just over a year now, and are expecting a child in June. Ever since we first started dating, his mom has said nothing but ugly things about me, and is always starting drama over petty things, or blaming everything on me. My actual mom (who was my best friend) died just a few days before Thanksgiving. As a result, on top of my existing anxiety and pregnancy hormones, I've been very depressed. She contacted me one day to tell me how terrible of a gf I am, and that it's my fault she treats me the way I do because I didn't come to Thanksgiving or Christmas with the family. But she was hateful to me long before that. Every few days I see something on FB that she's posted about me, and it stresses me to a new level. Any suggestions? The bf/baby daddy has said something to her before, but she always changes the subject and he lets it go. What do I do?