You sound like a such an amazing guy and like you would be a great boyfriend so I think you need to walk away from this because she doesn't seem to have relised this ever! The best thingis to go back to no contact and start new. Try new things and meet new people! It will help a lot! Befriending her will only make things hard on you and easier on her. You should want someone that won't walk out of your life but will fight to stay in it and be yours!