AITA for not forgiving my female cousin for helping my ex cheat?

To be honest, I just wanted to put my past all behind me and forget about it. However, my aunt will be visiting my city this weekend to attend a sermon, and bringing her daughter, Kaylee, with her. I’ve been dreading it all week and whenever the topic of us potentially meeting or hanging completely infuriates me.

For context, we’re both the same age, and I meet my ex through Kaylee. Without going much into detail, meeting my ex was the worst mistake of my life. Not only was he a pedophile for dating me when I was only 16 while he just turned 20. He was also verbally, emotionally, and sexually abusive by coercing and SA’ing me in my sleep. The one year I was trapped by this man was my rock bottom, I fell hard in school, was constantly depressed and suicidal, and felt truly isolated from the help and therapy I needed because I had to block all of my friends. The breaking point was when I found the hundreds of text messages of him cheating on me with multiple girls across all possible platform imaginable. I was heartbroken, especially since I had stayed loyal to him all this time while not receiving the same grace.

With no one to turn to, I bawled my eyes out to Kaylee, mentioning the texts and photos I found. When I specifically mentioned a girl with blonde hair, Kaylee began laughing and told me she knew who I was talking about. “Is this the girl?” She asked, sending me a selfie of the exact girl from his photo. She then told me how my ex had told his plans to cheat on me, which Kaylee neither stopped or had told me. This was months ago and she had waited all this time until now to tell me. I cried and asked to know why she wouldn’t tell me, she simply said “Y’all are both my friends, and I’m not a snitch”. …I was her freaking cousin, her own blood, we used to make disgusting love potions together, have sleepover, built a tiny cabin during the summers, and bonded over whatever dumb stuff we found funny as kids. This horrible man, who she have only met once in real life, whom she met through snap chat and has not had one meaningful conversation with, is on the same level of importance to her as me. Yet, I never confronted her, I never called on her bullshit and decided to cut contact with her after the break up.

Fast-forward to the present day, I had moved to her state about a month ago. The breakup was last year, but it felt like a lifetime ago with how much I’ve been thriving, living, learning, and maturing. To welcome me, Kaylee and her family went to pay a visit. When I saw her again, I did not make a big fuss, I was friendly, and cordial because I did not want to cause tension between my father and his sister (Kaylee’s mother). We did some catching up, and once again, I found out that my ex and her had been texting all along. Bad mouthing me, stalking me, her justifying what he did and feeding into his delusions that I still had feelings for him. I found out how an old friend of mine from high school had even reached out to him to talk behind my back. I should have said something then, about how horrible she is as a person, how much I despised her, expose her true colors even though it’s not much of a secret to our family. However, I took the high road and brushed it off like it didn’t bother me.

That night, I reached out to my old high school friend, we had a long conversation about why she did what she did. Although it doesn’t justify or dismiss her actions, because she had knew the full scope of what my ex had did, I decided to forgive her for taking accountability and we both became great friends once more. However, I will never ever forgive Kaylee, not in this life, not in any lifetime where she is my acquaintance. I had never hold a grudge before, because I don’t like having hate in my heart. I had forgiven anyone that had did me dirty, my best friend who had backstabbed me, the girl who had talk shit to my abuser, but I could not forgive someone who is out to hurt me, their own family and had never once muttered an apology or acted remorseful.

While Kaylee’s family is oblivious to my hatred towards their daughter, there were other families who knew. My older siblings and another auntie, who said they never liked Kaylee and thought she was a horrible kid and brings shame to the family. My father, who knew but doesn’t voice his opinion on “teenage business”, and my mother, who told me to just let it go. My mother’s words honestly felt like a stab, I told her about Kaylee’s betrayal with so much pain in my voice, but being the peace keeper she is, doesn’t make it clear who’s side she is on. It is never a competition and I don’t want to tear my family apart over this, but knowing that one family member had already betrayed me, I don’t need another.

I know I’ve been rambling for too long. I’m honestly writing like a maniac right now with all the anger built up in my chest and tears in my eyes. I’ve not told anyone all of this for so long that I just can’t help it. The mention of Kaylee’s name, and recalling what my ex have done to me refresh old wounds that never truly healed. I don’t want to see her this weekend, I never wanted to see her again, whether it be my graduation, my wedding, holidays or even on my death bed. My mother makes it sounds like I’m crazy for holding this grudge for something so “trivial” but she never heard the full story, of what my ex did, of how Kaylee is still doing me dirty until this day. AITA for not forgiving my cousin?