Fiancé’s grandmother drama seeking (advice)

So me and my fiancé are a younger couple (both 21) I’m currently 22weeks pregnant, we’re expecting our baby boy in November. About 2months ago we moved in together to prepare our lives and everything needed for our baby on the way, we have been doing good. Before this we had been together for 2 years but I was still living at home in a bad situation and he was still living with his grandparents at the time, Well it seems like ever since we’ve gotten our place and have been doing what we need to do his grandmother just can’t stand it. When I first met her I could tell she was just a fake old women, hate to say it like that but I call it how I see it & sometimes you can just read people. Like the type of person to overly compliment you & be nice to your face but talk about you behind your back, I can’t stand people like that. When we initially told his grandparents we were expecting I was around 7 or so weeks so very early but wanted to get it out of the way. She was rude & hateful at that point so I stopped communicating with her and didn’t come over for a while, maybe 2 weeks or so after that she kept trying to call me and text me and would leave voicemails about how she was “so sorry” & didn’t know what came over her this that and the other. I really could have cared less what she had to say but I ended up giving her the benefit of the doubt because of my fiancé. Anyway things were fine after that, I still knew she was fake & didn’t believe anything she said because she wanted to act so happy about baby then & be “nice” well fast forward to maybe a month or so ago we were over there staying a few days trying to get the rest of his things over to our place and get everything settled, now let it be known that I have NEVER said or did anything disrespectful to this women in any way shape or form, well that day we were leaving she completely flipped out about how she didn’t want this for him (my fiancé) & that this isn’t how SHE wanted his life to go(tf???) & she was talking about me & him very unkindly & even about our baby who isn’t even physically in this world to defend himself so that’s when I stepped in and said something because she is not going to disrespect my child and call him a mistake & this and that being a 70+ year old women preaching god and Christianity but being the biggest sinner I know. Like all she does is sit on her couch watching tv literally all night she will barely sleep, gossiping about people & smoking pot while taking 10+ medications a day & wonders why half her family wants nothing to do with her. Anywho after that I cut off all communication with her on my end because I understand that she is my fiancé’s grandmother and he can communicate if need be but I do not have to, so I haven’t spoken a word to her or seen her since then. Well recently every time my fiancé has been at work & she’s come in there (he works in a store) or has been over there to grab mail it’s like she has always had something to say about me or us negatively or has literally started arguments with him over me when like I said I’ve had nothing to do with her & that’s probably what’s boiling her blood tbh, and the fact that we have made a family of our own now & he’s not there to cater to her every want & need. At this point I just take it with a grain of salt because I’m tired of it & im not the type of person who likes drama or wants to deal with any more stress on top of what us soon to be mothers already deal with. Well tonight my fiancé is sitting in the living room with a few of his friends & she literally calls him out of nowhere at midnight and starts telling him to tell me that all she wants is once the baby is born is to get a DNA test, now this just pushed me over the edge out of all the disrespectful things she has said to and about us this is just the icing on the cake for me, insinuating that I cheated on my man or that I’ve slept around with people in our relationship (that’s how I took it) & mind you he knows for a fact this baby is HIS & we are very happy about it, he even got into an argument with her & told her that over the phone but the fact that she called and said that at midnight meaning our life is consuming her mind this much? It’s absolutely crazy to me. I have bit my tongue long enough and I am tired of this women disrespecting my family when she has nothing in her life together. Long story short I’m just writing this because I don’t have many outside perspectives or people to talk to about these things, I just wanted advice on what you would do or say in this situation or how you would go about it. I have done the whole leave it alone scenario & clearly she just can’t stop. Any advice is welcomed, ty in advance if you take the time to respond.