How do I deal with my stepmum despite all this?

My stepmum came along when I was 4 years old, about a year after my mum died. At first she seemed alright and we got on fine but over the years her and my dad began to argue more and my relationship with her gradually got worse. I admit to having made mistakes that upset her but it seemed like she just hated me for being me and I was stuck with her and nowhere to hide whenever my dad was at work. Her anger problems very rarely resulted in anything physical but I had a large amount of verbal abuse hurled at me and it hurt. A lot.

Her and my dad had two children with whom I get along really well but they are close to my stepmum so I don’t want any conflict with my stepmum to get in the way of that. But even with simple things like taking my brother to school or helping him with his homework she still lacks the patience to avoid losing her temper. And even though I don’t step in because it always makes the situation worse, I feel bad for doing so because it almost feels like I’m letting him relive what I went through.

But it’s not just the anger issues which have been a problem. She frequently organises things behind my dad’s back when he really should know about it and I can see him getting annoyed. She’s been told that we’re tight on money at the moment but she just can’t help herself to spending my dad’s hard-earned cash as well as what she earns, which is why towards the end of my first term at Uni I was shocked to find out that my dad had nothing in his debit account to send me and I would have been completely penniless for two days if I hadn’t been able to eventually access my savings account.

When I came back yesterday from my first term I greeted her immaturely. I’ve shown her little respect because I guess I spent too long thinking about how little she seems to respect everyone around her. I don’t want to hate this badly, but I don’t know what to do about it. I don’t want her to hate me. I’m surprised I’ve lived through it this long. All I want right now is to have a nice Christmas break with my family. Any advice?