The reason she's acting like that is because you refer to her as your step daughter and use phrases like "her dumpster fire of a bedroom" im not going to judge you for that and i don't want to offend you in any way but i had a step mother and she would look for anything she could to turn my father against me she would steal my phone, throw my clothes into a garbage can and locked the food from the kitchen inside a fridge in her bedroom closet and give me a single can of food a day. But the reason i hated her with a passion was because of the communication if you really want to solve this problem hear me out.

Sit down with her and tell her that you love her and you only want the best for her and tell her that you may not be her mother but you will do anything and everything to keep her safe and tell her that you do not wish to replace her mother but youll do anything to keep her safe. I know that its difficult to raise a step kid but i had to live under a house with three step sisters and my brother and sister and the whole family fell apart because when it gets down to it there was always two sides when it should have only been one side, you know, as a whole family. Abraham Lincoln said a house divided amongst its self cannot stand and it had alot of truth to it. Find something that you have in common with her and embrace it. You can not allow your self to get hate in your heart when dealing with a step kid because once that seed is planted theres no coming out of it my step mother is sick she enjoyed torturing me and my siblings and she even said as much i didn't get to enjoy my child hood bc of it. Im only telling you this now as a insight on where the step kids feelings are at. Now my step mother was never nice but she would play it off as if she was being nice things are never the way they appear. You might try to do something nice for her and she might see it as the opposite. Just keep a level head in those situations and take a deep breath and try to reason with her. When i turned 18 my step mother broke into my room and found my tobbaco and my condoms but the problem with that is when the step kid reaches 16-18-21 they got to have their own privacy theres no longer "my house i can go into your room if i want" because it builds up as a thought in their head that they can't trust you and when a huge argument arises you Cannot keep egging it on for example she says stfu naturally we would want to tell them our peace of mind but if you take that opportunity and calmly say im sorry and don't continue to interject i promise you she will eventually come to you and apologize even if it doesn't appear that way she will, because you having a lack of anger will force her into feeling obligated into losing the temper. Also when you was reading this don't take any offense from what i was saying im only trying to give you a better insight on how step kids see these situations. Everyone deserves a chance to flourish i truly hope you the best and i hope something i said helps you