Hello! Please remember that my responses are informational only, we are not establishing a therapeutic relationship.
It's always painful to be dropped from what seems like a meaningful friendship.
With regards XXXXX XXXXX #1: My first thought was that in order for someone to stay in a relationship with a married man for 25 years, she would have to be in great denial as to how destructive that type of relationship is. By you commenting on your concerns, it momentarily snapped her out of her denial, and she had to face the truth, even though it was momentary. The solution to going back into her denial is to get rid of the "mirror," (you) that showed her a different reality.
Friend #2 --I can understand that you probably got really, really scared when your husband got sick while you were on a trip (especially given the history of stap) --that makes a lot of sense! However, would it have been possible to call her sooner? It does sound like she was waiting to hear from you about solidifying plans.
So --I understand her being angry in this situation, however, I don't understand her not being able to forgive you for not calling in a more timely manner, and for not being a little more understanding of how scared you might have been about your husband. I wonder if it was too threatening to her to work out the conflict between you.
So --those are my thoughts --some people throw away relationships when their beliefs about their behavior are threatened (#1), some people will throw away relationships when they just can't face up to dealing with conflict and unpleasant emotions (#2)..