You may be in for one heck of a wait. You say she left because she was feeling unhappy. Did she give you some hint as to what might improve that situation? If not, you might want to ask her that if you are interested in having her participate in a reconciliation. Perhaps she is not the only one who needs to come to his or her senses.
When someone leaves another person, it can be difficult for both people. You need to give that person space. Talk to them and tell them about your boundaries. You need to decide for yourself, how long you are willing to wait. Six months is a fair amount of time, for someone to put their life on hold, while the person tries to figure out their life.
If she's leaving you because she's not happy, maybe you are the one that needs to take a step back and ask yourself why she wasn't happy. Then try to figure out what things you can do/change that will make her happy.
If she got the courage to leave, she's not going to come back, unless you give her a good reason too.