Sadly, what this kid needs is a dose of her own medicine. She needs someone to treat her the way she treats others. In this "politically correct" day age though, it can't happen. If you were to chew her out, slap her hand and walk her home pulling her by the ear,
you'd get in trouble
I think you've done the right thing, and the only thing you can do for now. That 8 year old is in for a rough life if she thinks she can get away with treating people like that. Take heart that if she keeps this up, she'll get the crap beat out of her someday!