Sitting on the pity pot will get you no where fast. Your zeal to have something with this female, even friendship has resulted in where you are now. Alone. Sooner or later for your own good you will have to realise that you have focused so much on what you want, you have ignored totally the bigger picture. She has a boyfriend yet she still sees you, and you took a date as a sign that the door was open and you could walk through it and she has slammed it in your face. Yet still she leaves it cracked enough to give you hope for the future. Your thoughts and actions have got you in a very unhealthy place and the only solution would be to take steps to get sanity back and heal. Leave her alone. I know that's not what you want to hear, but unless you do, and start putting your life on a better track, chasing after her will make an enemy of you, and leave you hurt and frustrated. Leave her alone and concentrate on other areas of your life and allow yourself to heal and grow, to make better decisions for yourself, and see things much more clearly.