In laws from hell need support

So my in laws have been horrible to me from the very beginning. My mil ditched me and went on vaca when I was having a d&c. Is super controlling and tries to get my husband on her side. My husband and I are seeing a therapist and we moved to the south to create some boundaries. We recently announced our pregnancy to his sister and mom. His sister sent me a message saying congratulations. I sent a very civil message back. His sister then told my husband that I assault his family, I am cold. She requested him to speak behind my back and then proceeded to text him novels essentially completely insulting my character and saying horrible things. Thankfully my husband is on my side. I’m just trying to be happy with my second pregnancy and I feel down that people would try to destroy my marriage and cause fights.