My Mum is being really horrible to me and I don't know why?

you're mum's not being horrible, she's just being unreasonable and not being able to see your priorities, tell her that right now, your revision is more important than washing up, and anyway, you've got siblings so surely they could do it for you. If you do that though, just make sure she doesn't catch you not revising, otherwise she'll never trust you, and she'll go ballistic