Depends on the couple.
You'll get tonnes of people on here saying 'No, it never works' etc etc. My boyfriend broke up with me after we had been together for 2 and a half years. Basically said he didn't feel the same about me as he had; we'd been in a sort of long distance relationship at uni (only an hour and a half away from each other but it was enough that we didn't see each other often) and essentially grew apart.
I was completely devastated, as, even though I knew things had been rocky, to me it still came completely out of the blue.
Nine months later (during which time we didn't speak to each other at all, not out of hostility but more a desire esp on my part to move on), he said he wanted to get back together. My initial reaction was 'No, it will never be the same; I'll never feel settled in the relationship' but I decided to give it a go just so I could look back with no regrets.
We're still together 5 years after getting back together (nearly 8 years since we initially started going out) and our relationship is great. We've moving in together next year and planning to get married at some point (not in any rush).
Sooooo... what I'm saying, in a long-winded way, is that just cos it doesn't work out for some people, doesn't mean it can't work out.
That said, reading your post, it does seem like you might have already made up your mind that you're over her, and the only reason you're questioning it is because she's upset that you don't want to get back together? If that's the case, walk away. It will better for you both in the long run.