I really feel for you OP and understand how you might be feeling.
My friend who is the kindest, most loving person you could ever meet met her husband around 15 years ago, he had a daughter around 12 years old at the time.
From day 1 the daughter been a nightmare. She is so selfish, self centred, jealous and overbearing…. My friend being the loving person she is loved her unconditionally still…. We as her friends and family respected that but I would actively avoid this child.
Over the years her behaviour escalate. She is always a victim that seems to go out of her way to make others miserable and you can see the satisfaction on her face when she has.
She very nearly ripped my friends marriage apart BUT they stuck together and made it through and in a great place now with very limited contact via the husband only. My friend had 2 boys when they met and husband has been the most incredible step dad, they also have a son together and are a very happy family all normal, loving and connected.
As mean as it sounds the daughter was always the issue and a vile human nothing will change. Now as an adult they have never worked, fat, lazy, messed up relationships and goes around wreaking lives all her family hate her but it’s all her own doing.
I hope you find a solution. Teenage girls are so hard but there is a limit on what’s normal and crossing the line. You are allowed to feel how you do, it doesn’t make you a bad person you are just being real.
My friends husband taking over ALL parenting saved their marriage. Take a step back and let him deal with it.
Good luck to you all x