Depends on what kind of a person she was/is. People change, make poor decisions, mistakes and such and learn from them.
I broke up with my first true love, treated me good and loved me with all his heart there at the end but there were little things I couldn't get past. I was 20, had a lot to learn. Almost 3 years later I realized I still loved him but he was engaged to someone he moved on with a year and 1/2 after me. I let it go but then when they broke up we had a wonderful night together, then he just went back to pining after her even after giving me hope of another start. Now he's back with her though they live hundreds of miles apart most the year. Took me over a year 1/2 to move on and realize I deserve better and come to the conclusion I was just a rebound. As long as I have that frame of mind I'm good. I am dating a wonderful guy right now, though he's overseas currently but I want to learn from the past and move on to the future.
That's all you can do man, just look to the future and know that you can find someone who can love you more and be mature enough to keep the love there and work through hard times.
In a relationship each person has to put in 90/10 of effort. Then nobody is left feeling unworth an effort. Each person has to put in 90%.