People i need serious help with this problem please?

ok well i new this girl in highschool her and her friends used to follow me around stalk me take photos of me harass me in all kinds of way well months later we graduated and i started talking to wone of them sfter months of talking to her i started to trust her i told her about howi was abandoned by my father when i was young and told her all about my past and told her stuff i never told anyone. i considered her a very dear friend. i began to fall for her but she liked someone else. i was crushed and kept my distance but ended up talking to her again cause i promised her i would always be there for her no matter what happened between us and i never break my promises. well after that i began to notice that she i was always the one to initiate conversations and that the very few rare times she started them she always conveniently had people over. i knew that this was probably a game her and her friends were continuing from high school but i wanted to believe that she was a good person someone i coul trust and not another person that didnt care about me. well after one of the toughest choices i had to make i decided that even though i promised to be her knight in crimson armor i couldnt stay in this situation any more. and even though my self esteem was destroyed after this i knew that i deserve better then to be someones toy. i know i dont deserve to be treated like this and that i deserve someone tht wouldnt swear to me knowing my past that they would never hurt me but i still think about her. this all ended months ago but i still think about her. i miss her. its not like i want to be with her. but idk it was nice having someone i could just let all my defenses down around. the f*cked up thing that always kills me is that even though this had such an impact in my life it didnt even impact her. all that happened is she lost her entertainment for a while. idk what to do anymore im happier now but at night when i get lost in thought or cant sleep she always poofs back into my mind and i hate it. please help i need to know how to get past this