A true friend will be there for you when you need them. They love you and care about your feelings. Their concern for you will carry you through some dark nights of the soul. They are a blessing from God and his way of caring for us sometimes.
A true Christian friend will also tell you the hard truth when needed. They will call you out on your lies. They will confront your sin. They will tell you honestly when you are being selfish and self-centered. They will notify you when you are being immature and need to grow as a person. They will not overlook your destructive behaviors because they want what is best for you.
True friends care more about you as a person than keeping you as a friend.
Sometimes in our quest to stay connected to people we care about, we look the other way when they are being unrighteous or ungodly. We make excuses for poor behavior or ignore things they need to change.
I know it is complicated to be in any relationship, and perhaps Christian ones are the most complex, but that should not keep us from seeking the good of the people we call our friends. If fact, I think it necessitates it.