If that's how she truly feels, there isn't much you can do about it. As is the sad pattern, most girls (maybe most of us) stay in a relationship longer than necessary, and when all love is gone, they dump you. There were probably signs that it was going downhill, but it always rips the floor out from under you. And therein lies the problem: we aren't being honest with how we feel and we are too insecure to be apart unless we know that we got something else lined up or the relationship is completely dead to them. And that is an immature relationship.
I don't see anything about begging to be back, so that's a plus. Most of us have that beg to be back afraid to be alone behavior and it's typical. You didn't do it, you aren't a typical guy, and that is a good thing.
So now's the time to really look back on the relationship and look at those details. What were some things that you did that probably were wrong? What were things she did that were wrong? You may need some true friends that aren't afraid to be honest with you to help you out with this. Or you can post them all here. I or somebody else will be happy to read and happy to help you.
This is a time of growth. An opportunity to become a better person. You identify the problem and you can now fix it. Dumpees always grow the most because they feel like the failure, and they want to be better. Dumpers usually feel like a winner, they got the bad out of their life it's the other's fault and now they are good. It's delusional behavior and not something she can really grow with as rapidly as you can.
Who knows when you might hear from her again? She hasn't forgotten about you and three years, trust me. The point is if she does pop back up, you will be ready. And when all this self analysis is done, you might not even want to be back with her. Why would you want to be with the same person were all her flaws if you worked so hard on yours? Don't settle.
Anyway, that's a big what if. We have to take it one day at a time here and what you do in terms of her is not important. This is all about you building your life without her and making things better for you and make you happy. The hurt sucks, it doesn't go away, and you can't help thinking about her. But it will make you stronger in the end.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.