You have realized that if you allow yourselves to be platonic friends you'll end up in the same game, an on and off relationship game. Let her know it won't be a good idea to be platonic friends. If it happens so you'll be wasting each other time as the two of you would end up together then break up. Thus, you should stop communicating with each other. You should cease communication because it's evident you were never meant to be together. While friendship is a good thing - returning to the state of friendship before you began dating - it is different now. It will bring back the memories and it will be hard to move on. In the months to come, the feelings for each other will have died thus you'll become casual friends since that is what you are meant to be. But, if you become platonic friends you'll be hurting each other and wasting each other's time.