What do I do if my best friend chose her boyfriend over me?

My best friend is going out with a guy and they really like each other but, he has a history of cheating on his girlfriends. So I found out with he was cheating on her and I told her. She talked to him about it and he denied everything. Now she is texing me and saying mean things to me like "You are such a skrew up" and "everything is always your fault" and "You dont mean anything to me anymore" and I dont know what to do. He is going to hurt her and she told me to lose her number and leave her alone. She just came to our schoo la couple months ago and I was her first real friend and we got really close. I talk to her about everything but she doesnt want me in her buisness. She blew me off to hang out with him and lied about it and I dont know what to do. Please help mee!! I dont know what to do anymore since everything is always my faultt.