12 year old attitude :(

I don’t even know where to begin. My 12 year old daughter is making me feel insane. Constantly rolling her eyes. Constantly stomping to her room and trying to slam the door (won’t slam because of carpet) I hear her secret talking crap to her sister. Life isn’t fair everyone hates her yada yada. This kid has never been without. She has all the bullshit kids nowadays want. Phone computer nice clothes. I feel like that’s part of the reason. I can’t take her phone away because she uses it for a medical device. She has type 1 diabetes and wears a sensor in her arm to read blood sugars and her phone responds to that and sends my phone constant updates. If it weren’t for this I would take it. She’s going into junior high in 4 months and I just feel like if I don’t figure it out this summer it’s going to get worse. Help.