Wow. This issue has been "thematic" for me in the last decade, or so.
Family members:
I was willing to give family members more chances because they are family members, but they too need to abide by the rules of having to learn. My last remaining parent caused a lot of (completely unnecessary) problems a handful years ago. It was completely UNnecessary. I was drained. Then it dawned on me, she had that exact same problem when I was a kid...all the drama was UNnecessary and a way for her to get attention. As applied to the more recent issue, since she interrupted what was a long stretch of peace, I have refused to make amends and our rapport is more business-like than family-like. I once glanced through a book on the display tables at B&N about "forgiveness" and it said forgiveness has to be earned. If the same mistakes are repeated again and again, my feeling is that the person has not learned and is therefore not entitled to my forgiveness. Or...I can forgive, but don't need to forget.
Friends:
I have friends that I've had since I was in grammar school and have never had problems with them. No problems. I, however, have had some problems with friends who encroach on boundaries more than they should. They have been told "not to go there," but they don't listen. I have one friend (picture a Madeline Kahn upper face with a Margaret Thatcher lower face) who I let into my circle of friends because we were in the same line of work. She constantly tried to set me up on dates with friends of hers. I told her "no way," especially since she seems to toss out my "checklist," but she kept on trying, probably because she knows my "checklist" wouldn't include her, so that's her sick way of taking a jab at me. Most recently, she e-mailed we with the same M.O. (I started a thread on "boundaries"). I did not respond to her e-mail.
OTOH, a co-worker needs to find a HOUSE for me. He is addicted to risk and buying/selling (even if it's bad), so he needs to spread his misery. I have told him repeatedly to back off (and others around here also resent the fact that he's such an intrusive idiot) but he seems to forget the reminder he's been given. I will no longer go to lunch with him and keep him at a distance.
Bottom line for your situation:
We don't have enough information, nor are you expected to provide it. You know what the short-term and long-term impact of your actions might be. This is where most of your "weighing" ought to take place. I've taken a tougher stance and have fewer friends because of it, but I should have chased them away earlier. So, in my case, I am detaching from a parent who is addicted to drama (and I'm the opposite - completely into organization and logic) and a couple of friends who need to push their co-addict/co-dependent agendas down my throat. These are not big losses.
I know you can evaluate the cause and effect of your personal situation. However, it ain't easy, so I feel for you. Good luck with it.