Midwifeinthe making, I find it very troubling that you say your friend has sinned because she got divorced. I know nothing of her personal circumstances, obvs, but some marriages are best ended.
My own parents should never have married. My father was abusive towards my mother, my siblings and to me. She stood by him. Partly at least because of their Catholicism.
Growing up in that family has left my siblings and I with major problems, severe depression, chronic anxiety, lack of confidence in the world. I see the greater "sin" (I don't use that word myself) to be them staying together acrimoniously (sniping, gaslighting, belittling, bullying), thus harming their children. Sometimes divorce is the best choice. And I suspect that without the pressure coming from religion (what would the priest think?what would the congregation think?) my mother might have chosen it.
I'm glad you feel happy rather than sad but I find your assumption that non-Christians don't feel as free or as happy as you both simplistic and arrogant: how can you possibly know? Personally, I feel much happier since I moved AWAY from religion. (And yes, I have tried several kinds.)