Annoying Not-So Family

So my boyfriend lives with his grandmother and recently I went to pick him up for school (to help him out a bit because before he was picking me up because I was trying to save gas until I got paid). I get to his house and he opens the door and gets his book bag and etc.. His grandmother comes out of her kitchen saying she was surprised to see me and asked me why I was there (I explained). She then started to talk to me about how our (my bf and I) sex life was her business and that my bf needed to stop buying condoms and going through why she has so much control over me too. I simply cut her off and said “can we do this later so him and I aren’t late?” she proceeds to cuss me out saying how disrespectful I was being to have interrupted her and I said “okay I’m not sure what you mean but I really need to leave for school” (him and I were cutting it super close). We leave (not by her command) and she took to Facebook (and called EVERYONE she knew) and told everyone at church about how I had cussed her out in front of his little sister (his sister was in the other room getting ready). Idk what to do because I only have one witness everyone thinks I’m a horrible person now and I’m afraid to go to church. What do I do?