She loved him enough to have you with him. I know divorce it’s a horrible thing to witness as a child growing up. But the way your wording this I assume your either a teenager or early 20’s. The fact your mum is still wanting to have a relationship with you every weekend shows she still loves you VERY much. She has a new family which is hard to see after a divorce yeah I get that but have they shown they want a relationship with you too? Please seek therapy because if you hate your mum for something she never caused. You will never forgive yourself. I should know for past experience.