Are all stepmothers life disasters and depressents ?

No, sorry you are stuck with the one you have but not all of them are like that. My ex-hubby remarried in 2006 which gave my then 12 year old daughter a 'step-mother', she's really kind to her and stays out of my and my ex-hubby's way when it comes to parenting. If someone were treating my child the way this woman seems to have been treating you, it wouldn't be a pretty picture for her.