Can’t be easy to see/hear that, and it sounds extreme, but I’m sure it’s just a variation on the tantrums we all experience from kids.Is it? She even hit/bit herself this evening and said she hates herself! Over the smallest thing. Just wonder if this is common or a sign of possible deeper issues.
My only advice is lots of positive reinforcement. Be sure to praise her for any good behaviour to the same extent or more than you’d tell her off for the bad stuff.