I can't know for sure but by going by your history, you two broke up twice which tells you that you are not meant to be life partners. She likely didn't say you may get together in the future to be purposefully manipulative, but rather to make it seem less harsh. Afterall it's scary to think that someone will never be in your life again so saying things one really doesn't mean to help ease the transition is common.
What you need to do now is accept that she wasn't meant to be with you for life (your history proves that) and work on getting to the stage of indifference to her. There is where you should be (at indifference) so that you will be able to have a clear mind and heart for the lady you were meant to spend your life with.
With zero contact, time and using your time productively will get you to indifference to her faster. First you have to accept that she's not coming back, that she's better off gone. If she wasn't better off gone, you'd still be with her.