I’m so sorry you went through this. You will be stronger in the end, I promise. I went through it. I had an ex who was with his ex girlfriend for an entire year while we were together. I was too trusting and wanted to ignore the red flags. Going forward, I was able to see those red flags in others and avoid a similar situation. And now I’ve been with my husband for many years and he is amazing.
It sucks. It hurts like hell. But you will be ok. Take care of yourself. It’s her loss.