I felt everything you've described when I met my little again all those years later. Like WildMermaid, I thought she was dead. She was soooo angry with me.
I have to tell you - this is evidence that the hard work you've been doing is working. Little feels safe enough now to show herself and even more, to show how angry she is. Your therapist will be so proud of you! I know how scary it is. You can do this.
It helped me to imagine an actual child the same age as my little, sitting in front of me. I'd think about what I'd say to HER. To any little girl in so much rage and pain and fear. And that's what I'd say. Out loud.
You said she's being mean to you. That's what children who feel safe do with their mothers when they are upset. She trusts you enough to show you how she's really feeling. And even if you don't feel you're ready for her, and for this, I promise you are or she wouldn't have chosen now to show up. It will be ok. It WILL be ok. You're safe and she's safe with you.
You aren't alone. We're here. And we're not going anywhere. Check in often. Both you and little you.