Emotions currently being stirred up

Even though it's nearly been 20 years since I cut ties off with am off and on friend and her mom due to the friendship being toxic and somewhat traumatic, I am currently working through it with a counselor. As a result, my emotions are being stirred up while I am talking about it with her. This friend and her mom pulled some really nasty and bizarre stunts on my parents and me and every once in a while, I am still haunted at what they did.

One situation happened 26 years ago when my friend and her family invited me to go camping with them for the 4th of july which I had looked forward to for a few weeks. When it came time to the camping trip, her mom decided that she didn't want me there. Instead of being upfront with me, she led me on and said how excited she was to have me there while asking to speak with my mom. Meanwhile, she told a bluff to my mom that she would be at the campsite alone with her two kids and didn't want to deal with a third. However, we drove in the night before the 4th only to find that her husband was there.

During the trip, her mom was very unpredictable in nastiness and rudeness.

A. She kept nagging at me about things

B. I asked her a few questions only to have her blow up at me

Well, we ended up having the cut the trip short because nasty weather was on the way and all the activities that I was planning on doing with my friend got canceled and I was mad. An hour before we left, we were at the general store with my friend, her mom and her half brother. While we were there, her mom looked at the shirts for sale and said "Each of you pick out a shirt in your size." I automatically thought she meant all three of us. Her mom said, "No you! These are for my kids." Here I had made my friend and my mom some little gifts.

There is a part of me that is still angry in the way I was treated but I am trying to live today and not let it bother me because that was a long time ago. However, why do this still seem to haunt me?