Do tu have a friend who tu deep sown just want to tell them to leave tu alone but are too afraid to do so?

I have this friend who is such a bully. She is violent and sometimes likes to hit me and our other friends in a "playful" way but it seriously hurts. Whenever we go out to the Mall o somewhere public she makes us meet her at her house so she can scope out what were're wearing then change immediately if she thinks we look better than her. Also she goes through our phones and reads all our messages, then when she sees its a guy we're txting she'll take their number and start txting them, pretending to be us AND she even sometimes sends pics of us to guys, pretending that its her (SOO ANNOYING!). I know the answer to this seems soo simple, STOP BEING HER FRIEND, but tu don't realize how scary she is. Shes very physical and verbally abusive and she always gets her older siblings to go after her enemies. One girl actually got beat up at the side of the road, one día after school, when my friend told her sisters that this girl had started dating her ex.

How can I get out of this friendship? I'm too scared to confront her because of what she is capable of but want soo badly to leave her and mover on .. PLEASE HELP!