So know this situation. Sorry that you have to experience it. It happened in our case as well with my mother. I don't have many positive input to add unfortunately, my relationship with my mother is damaged (from my point of view for sure, I haven't heard her honest opinion yet) and I feel distant and defensive. The confrontation happened a year ago.
But it got better after the first weeks. She came around to just ignore our relationship 'arrangement' mostly and doesn't talk about it nowadays. Give your friend some time, maybe it will become better but if I would be in this situation again, I would (after some time has passed) point out to the other person that this has damaged my picture of her/him and that I am disappointed and hurt. Not in an aggressive way, but I believe that my mother for instance is sure that I am the only one at fault here and that she has every right in the world to hold my life against me in whatever way that pleases her. Still some conversation to be had for sure in the future, but as she has been quite ill and just completed her treatment it wasn't appropriate to stress her even more, from my point of view.
Wishing you a better outcome than I experienced.
Facts: 30, female, bi, v-type relationship with Sward (husband, straight, mono) and Lin (boyfriend, straight, mono), poly-fi and co-primary.