OP - I have been where you are. From 11/12 I had 3 years of dd utterly hating me, wishing I was dead, distancing herself from the rest of the family hating her siblings, sneering and snapping at all of us each and every day. I used to get up with a hard fist of fear in my stomach wondering what she was going to do and say. We all walked on eggshells around her for years, she was so volatile and full of hatred for us.
I took it very personally, and I really shouldn't have done. My relationship with dd prior to this had been great - we were very loving and close. Her adolescence was like a huge, all engulfing hurricane that blew away everything good in our relationship and everything I thought I knew about myself as a mother. I couldn't show her any love or affection without having it thrown back in my face, and I ended up withdrawing and becoming cold towards her. Unless you've been on the receiving end of that level of hatred for years on end it's hard to understand how devastating it is. You can read all the parenting books in the world, but as a human being it's very hard to rise above daily abuse that goes on for months and years, even if it's your child who is dishing it out.
Anyway, what helped was:
The teenage board on mumsnet (I know she's not a teen but she's obviously going through adolescence) - just to let of steam without ending up having responses from a whole load of people who've never been through it themselves but are happy to make judgements about your parenting and advise you how to behave
This book here
Eventually CAMHS and social services, plus support from dd's school.
My wonderful, steady, loving DH, who maintained his calm even though on occasion her behaviour made him actually cry (the only time he'd shed tears in 20 years of our partnership).
Oh and most importantly, the passage of time. She is 16 now and tells me she loves me several times a day, and calls me her best friend. She still says she hates me once a month or so, but she says sorry shortly after.
Basically, buckle up, try not to withdraw, love her as much as you can and HOLD STEADY in the storm of her adolescence. Don't show her how upset she's making you. Don't try to guilt trip her, it'll make her worse. The more difficult she is the less likely she is to admit fault when she's confronted with how her behaviour impacts on her family. Say your piece calmly and then walk away.
Oh, and I'd massively limit her screen time. She'll 11, you can make that work. We let the genie out the bag on that one and I sorely regret it.
Good luck!