Father’s new partner – Not sure how to see this situation differently

My parents were married for 40+ years and separated after my mom found out he was having an affair. I witnessed everything because I lived with them when it happened. My mom was distraught and I wish I could have taken all of her pain away at the time. I was very angry with my father at the time and I stopped talking to him for a while when my mom was alive. I looked up to him as a man and I never thought he would do that to my mom. As an adult, witnessing how this transpired is still affecting me to this day as it shows up in my relationship. I am blaming the woman that he is with today for my parents separation and I don’t see myself wanting anything to do with her. He asked me the other day if he could bring her over to the house for Thanksgiving and I explained to him that I do not feel comfortable with that. I respect and understand that he has moved on and needs a companion at this stage of his life, but I am just not accepting of this woman. I’m not sure how to move past this. I know it makes him feel bad but then my thought is, well why should I be okay with this after what you put my mother through! I know ultimately it’s not about me, it’s about him and the choices he made. I was close to my mom and seeing how the separation affected her and then going through cancer was life altering for me. This is what I came up with for models, I know deep inside I would like to believe the intentional, I just don’t know if I can. It’s been 6 years since my mom passed and I am still feeling resentment towards this woman that I believe was the cause.

C – My father asked if he could bring his partner to the house for Thanksgiving
T – I don’t want her there, she is a home wrecker
F – Resentful
A – I tell my father how it makes me feel, I don’t have a relationship with her, I continue to blame her for contributing to what happened with my parents
R – I stay resentful and I don’t want to have a relationship with this woman

C – My father asked if he could bring his partner to the house for Thanksgiving
T – It’s possible that she wasn’t the woman he was with at the time
F – Curious
A – Have a conversation with her, forgive my father and the woman or women he was with at the time, forgive myself for holding on to this anger and pain
R – Becoming more open to the idea that I can accept her