What do i do about an annoying/ immature friend?

Im 13 and i have this friend who is 15 and she is really immature. She has the maturity level of a 9 year old, and we're going to 9th grade this year. I tried to address this to her before but i was accused of "cyber bullying". She also dresses like a 4th grader and doesn't know how to do her hair. She is african american and she thinks she can cut her own "bangs" and always wears a stupid headband that never matches her outfit. Her clothes are also a lost cause; one day at school, she wore a green t-shirt under a cream colored cardigan with pink earts on it, and jeans that came up to her ankles. I'm so embarassed to be with her because shes so annoying/ immature and ho she dresses. I have no idea what to do about her. HELP!