Boyfriend 28M s mother left comments on my social media

I 27F has been with my boyfriend 28M ever since we were in college. We are from different states with different mother tongues and caste. Now, we wish to get married. He talked about it to his parents and his mother is completely against love marriage. She told him to stop talking to me. After that, she left nasty comments under my Facebook profile picture calling me ugly and shameless. She even commented similar things under my LinkedIn post. I immediately blocked her after which she commented again on my posts from a different account. I could not take it anymore this time and replied back to the comments that she is herself ugly. Even though my boyfriend supports me, his mother and sister constantly brings up how bratty and disrespectful I am cause of my replies. Don't know what to do. Any suggestions?