Sorry my friend but I am going to have to throw a few cliches out there. Firstly, give it time. IMO you are doing all the right things. You are very aware of your thoughts, are keeping busy and recognise that there will be good days and bad days. At the moment because it is still fresh you are having more bad days than good, but this will turn around. Trust in that. And also, realise that 'this too shall pass'. Be kind to your grief, let in, make it your friend. If you wake up and realising you are thinking of her don't try and push the thougts away. Let them be. Often we suffer and stress more simply because we can't get rid of the negative thoughts that arise. But why should we? We don't try and push happy/positive thoughts and feelings away so why are we so dead keen on being nasty to our negative thoughts and emotions, including grief?
As for the why, when, how etc of what happened it truly is in the past ((sorry another cliche!). Staying in the past is preventing you being in the moment and moving forward. Again it is ok to feel sad, and ripped off and cheated by the things she said/did but don't let your knowledge get in the way of the truth of the situation. She has her reasons for doing what she did. She still has control over you from a distance too. Free yourself from her. In your mind, wish her well on her new journey, forgive her and then forgive yourself. Only then will you truly move on. Good luck.
Some people are drains and some are radiators... Keep clear of the drains and hug the radiators!