Some may think this sounds arrogant, and you can call it what you will... but I cannot answer this one with an actual person, because I have learned the art of filtering my relationships as I have aged.
I wish it hadn't taken me so long to realize that in relationships and friendships, you have choices. While the relationships I have with others should not be all about me, I have the freedom - and so do you - to only allow healthy relationships in to my life. If you are not good for me (or my family) or if I am not good for you, it ain't happening.
Because of the degree that my friendships/relationships built or tore down my self esteem and confidence growing up, I have already tried to encourage Audrey (age 12) to realize that there are some 'friends' in her life that are good for her and those who are not so good, which is so incredibly difficult when you aren't quite a teenager. I know it seems harsh, because kids are kids, and girls are girls and all around, they can just be mean... but I don't want anyone in my child's life that will negatively impact her self image.
Relationships matter, and they certainly aren't always easy. But, working through the difficult times with a true friend is different than tolerating the shenanigans or trying to correct the abuse in an unhealthy relationship. Sometimes, you just need to break ties to cut your losses.