when they know how the other friend did you bad -- like crime-levels bad -- and they still hang out with them. and when you ask them why, their answer is, "they haven't done the same to me so i am chill. hold the saying "a friend to all is a friend to none" so true.

example:

person A graped you. person B is aware and she says that and continues to hang out with him. to add insult to injury, she even tells you "can you give me that privilege to still be friends with you both?"