My sister has a 3yr old with her ex. He's an emotional abuser. (Telling her she's fat and who would want her etc etc etc)
Anyway they have been split up over a year. She has a new boyfriend who is really lovely, Down to earth and has taken to her son like his own.
This weekend she went to mums with ex boyfriend in tow. Her excuse is 'we have a son together why can't we spend time together' yet he sits there berating her, making her look two foot tall. When he says owt to him about how he needs to lower his expectations of life (he's skint and going through catalogues and looking at £1k beds and sofas etc) when she mentions that he needs to start low and take an offer of our cousins sofa which is selling at £30 she gets told to 'shut up little girl' 
AIBU to think that if she fucks up her new relationship because she can't cut ties with her abusive ex then it's her own fault.
I get told to shut up because I don't know anything 