Trying to be civil😥

So basically boyfriend has two kids, one with me and one with his ex which he didn’t have the best relationship with and fully admits to his wrongdoings in the relationship however his ex doesn’t admit her wrongdoings in the relationship and acts like it was all his fault so they don’t get along at all but I have tried so hard to get along with just for sake of the kids since her son is my daughters sibling and I would love for them to have a relationship but lately I’ve noticed these little things she does like we both follow each other on Instagram and whenever I post something cute about my daughter or boyfriend she will make it her mission to post something with her son or her fiancé the same exact day and at first my boyfriend thought I was being a little crazy till we tested it out by posting a photo of him with our daughter and not even an hour later she posts a picture of her son w/ her fiancé also she tells me a lot of times a bunch of untrue stuff about my boyfriend like saying he’s a pathological liar or how he supposedly cheated in their relationship (even though when I asked her about it on a later date she admitted to just assuming he was cheating) and basically tries to convince me to leave him so a couple days ago I straight up asked her why she does that stuff and sent me this long message of how I’m supposedly settling being with my boyfriend and I’m afraid to leave him just because he’s the father of my child then was saying that my boyfriend supposedly told her that I stress him out and he would rather be homeless than living with me so when I confronted him about it he showed me the messages and she was lying about it. I just genuinely don’t know what to do anymore because at this point it seems like she doesn’t want me with my boyfriend even though she literally has a fiancé and it has overly stressed me out because all I have ever wanted was for us to get along and be able to all do things with the kids when they get a bit older. Would just love some advice from you girls on what you think I should do because at this point I just want to give up and block her from everything but I also don’t want to do anything that will affect my daughters future relationship with her brother😭