How should you break NC? Just call her. As for getting back together, it sounds like there was no major issue for breaking up in the first place except for her being busy. But I read that as you not being comfortable not being the center of her attention. Make sure you understand that you are a part of her life, not the only thing in her life. Don't be needy or demanding. Understand that she will get busy again and think about how you will react to that.
Just be open and honest with each other and understand that if it doesn't work out, it isn't the end of the world.
Good luck.
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