Unable to understand why my (M40) wife (F38) still keeps karwa chauth vrat for me even though she has cheated on me and is in relationship with some other married man.

I am a 40 yrs old male, got to know 2 yrs back that my wife was having a extra marital affair with her boss, I was devastated and heartbroken at the beginning but later when i started coping up with the situation I realised that I will never be able to love her the way I always did and I offered her to take divorce on mutual concent but she refused saying our kid will go through a lot of trauma. So we have decided to stay married for sake of our daughter, and over a period of time I have accepted the fate of my marriage and moving on with my life, but I am unable to understand why does she always has to keep karwa chauth for me when she is clearly in love with someone else, why does she needs to pretend that all is well in her married life. We stay in different cities now and she always video calls me to open her fast. I just feel disgusted by the way she behaves as if I am her one and only. I am not sure if I am looking for any suggestions or just want to let this off my head, but since it was karwa chauth so just thought of sharing.