Why would my ex boyfriend's new girlfriend want to harass me and talk mess without any reason to?

i get harassed from my ex bf's new girlfriend all the time especially over twitter, and the sad part is I don't give her a reason to talk shit, and what I mean by that is I completely moved on from my ex I dont call text or even talk about him or her. I guess she just wants to try and ruin my life by dangling my ex in my face. Now my ex does not have any accounts on social media, but i do know that i always have this gut feeling he is instigating it all and still talking shit about me bc why would the new girlfriend till this day continue to say she knows me when she clearly doesn't, and talk about my past relationship i had with him, saying things like "he only fucked you over cause you let him lets be honest". throughout it all he sits there and plays the victim saying both of us are childish when i know for damn sure he's being shady and childish as well especially if i confornted him about it and he didn't want to answer the call but answers my friend text telling him about the bullshit that was going about his psycho girlfriend. I've been ignoring her and him, but its getting to the point I'm about to go off. I've moved on, but for some reason I can't fully be at peace if this girl is still bringing up my past with him which i find odd. like my ex literally gave her my number to call me on private and leave me stupid messages. Im not gonna lie I know she is threatened and insecure. but my main concern is that he needs to pacify his bitch.
Why would my ex boyfriend's new girlfriend want to harass me and talk mess without any reason to?
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