Hanging on by a thread

Oldest is turning 12 tomorrow....she is becoming a woman right before my eyes. She is beautiful, charming, smart, vivacious and right now we can't hold a conversation without yelling at one another....and the looks....she no longer hangs on my every word, I am not her hero anymore, I am not the one that can make everything okay. I am now the enemy, I am the dream crusher, I am the happiness destroyer. We used to laugh....and talk so much Youngest could barley get a word in. Now we drive to school in complete silence.....I can't look at her without getting angry and she can't look at me because I have disappointed and confused her......How did this happen, why did this happen? I never wanted my kid to look at me the way I looked at my parents...why did I think I could escape that? I thought that she would always come to me when she was down...tell me when something was bothering her....if she was scared. Now I feel like she doesn't want to tell me anything...and if she did would I even hear her right now? My heart is heavy and all I can do is cry. I hope we make it through this part...right now I am feeling weary and beaten. For the first time in 12 years...I feel like I am failing Oldest and this feeling sucks.