My Mum keeps telling me that if Dad hadn’t screwed things up we’d still be living in our old house and wouldn’t have to worry about every bit of money we spend. My Dad did screw things up and I’m really angry with him, but every time Mum says this I want to scream at her, its not fair.
It sounds like your Mum is feeling stressed and probably a little bit worried about making sure she has enough money to do what she needs to do for all of you. But it's not great that she's telling you that your dad screwed things up.
Most young people love both their parents (they hate them both at different times as well) and it doesn’t help to keep putting your Dad down in front of you. It might make you feel like you have to pick sides - either your Mum or your Dad. But you don't have to do this.
Let your Mum know that you’d like it if she didn’t talk about your Dad like that and that you love them both.