People change. Jobs will move a person to act differently. The birth of children will wipe a smile or two off a new parent's face. Divorce will bring on a troubled mind. So many negative life events will cause people to put a halt on being kind, sweet, loving, and the type who will have your back when times are rough.
When one is told the truth about a favorite family member and friend, the person will act defensive. They will act as if you are the trouble-maker for exposing truth. They don't want to face the fact that someone who might have been once a best friend is now toxic. They find it hard to fathom that a "best friend" would act in ways that aren't friendly. When scandal from long ago rears its ugly head, they don't want to believe that their loved one really didn't like them very much. The truth is a hard pill to swallow.
The best thing we can do when we see that family members and friends are esteeming people, who are no longer in their corner, is to gently remind them that they now have the power to do whatever it is they desire without the need of hand-holding from XYZ. We can also point out when the person said or did things that wouldn't constitute a good friendship. Once the opportunity has passed to speak truth, one must keep a lid on his or her mouth and let the truth marinate on the person's mind, body and spirit. Hopefully, in time, he or she will wake up and realize that the favorite family member or friend just isn't the same.