Was I wrong for leaving after she cheated years ago? Should I go back?

I really need an outside perspective because my emotions are all over the place.
My ex and I started dating in 10th grade. She was my first relationship, while I think I was her second or third. During our relationship, I caught her talking to other guys a few times. Nothing ever seemed serious, and because I loved her, I chose to ignore it and move on.
We were together for about six years. We had both agreed that we wouldn’t have sex until marriage, and I genuinely believed we were on the same page.
Then I moved to another country for higher studies, and we started a long-distance relationship. About six months later, she got a part-time job back home. She became close to her boss, and one day she and her coworkers went on an overnight trip to a hill station. During that trip, she slept with her boss.
What hurt the most wasn’t just the cheating. It was that after six years of us choosing to wait until marriage, she slept with someone else within a matter of weeks of getting close to him.
I started noticing changes in her behavior and eventually figured out she was seeing someone else. Around the same time, she had also applied for a student visa to come to the same country where I was living.
Her visa got approved, she moved here, and we had a huge fight. She ended things with the other guy and asked me to give our relationship another chance. I did.
We lived together for another two years, but I never truly got over what happened. The anger, betrayal, and loss of trust never went away, no matter how much I tried to move on.
Eventually, I developed feelings for a girl at my workplace. I didn’t act on those feelings immediately, but about six months later I started a relationship with her. At that point, I ended things with my ex for good and asked her to move out of my apartment.
Now she’s telling everyone that I cheated on her. None of our mutual friends know what happened years earlier because she has never told them about cheating on me with her boss. As far as they know, I’m just the guy who left his girlfriend for someone else.
Recently, she’s been begging me to take her back.
So here’s my question:
Was I wrong for ending the relationship the way I did? Should I even consider getting back with her, or is this something that’s better left in the past?