What you've written in your post is upsetting, but I also think it's good that you've started to recognise there's a problem, and reached out for help.

First things first: please remember this is a seven-year-old child. Not an adult. Not someone with a fully-developed sense of the world, of themselves, or how to behave themselves in the world.

Children are extremely attuned to the adults around them. They pick up on feelings. Your stepdaughter will know how you feel about her, and will be reacting to it. So she has done some bad things. What kid hasn't? What kid is perfect, and never ever makes mistakes?

You are talking about a little girl whose parents are not together, and whose family is divided into warring factions, and instead of feeling sorry for her, you say you hate her. That is a displaced emotion meant for someone else.

I was particularly struck by this part of your post: "When all of this happened at first my husband agreed it was just too much drama to have her around, but he changed his mind and now insists on having a relationship with her and having her over a lot."

Are you talking about your stepdaughter here? Your husband decided it was "too much drama" to see his own child, then changed his mind about having a relationship with her? And she's acting out? And you're surprised?!

You don't have to "be mean" to her. She already knows how you feel. Her behaviour makes that clear.

I think you need to get your family into therapy, pronto. Your stepdaughter is a child and cannot change the situation. You can.