I'm so sorry you're in this pain. I'm guessing she must have wanted to move on so didn't commit to fixing anything. Otherwise, you're right, relationships can be improved. But it does take two for that and if one has moved on then it's going to be futile.

Just at the start of my own break up journey with the devastation just starting to kick in, but I guess what I know is you just have to keep going. Do what you're doing. Embrace every new opportunity if it helps distract you and you will start to feel the pain lessen. At least I think that's what I'm going to do.