What should i do?

Im a male 21. Theres a female whos also 21. I just need help kinda bad with what to do about the situation in hand. Heres the story. There is this girl who ive known since highschool. Weve always been pretty close. When we 1st met i thought dhe was attractive but that was it. But we just got close. She was always there for me and i was always there for her. Shed text me daily without me even texting back or anything just to see what was up & always told me how special i was to her. Finally after awhile i just began to get feelings for her. Began seeing her a diffrent way and everything. But she had a bf. Who I myself hooked her up with. They dated about a year. But they broke up & well after that i figured it was my shot. She was still textin me daily & would still tell me how she never had a dude like me. I figured i wasnt in the friendzone cuz she never talked to me about her probs, relationship or anything. When we were together it was just about us. So i asked her out and she told me she didnt see me that way & only as a friend. Yet after that shed still act & do everything the same. But i couldnt. It got to a point that i could think about her only & when i seen a couple it pissed me off. It was eating me inside. So i said fk it and just stopped communicating with her. Nomatter what she did i just would not communicate with her. Even if shed smile at me id pretend like i aint see her. Then she just texted me outta the blue and told me that she just couldnt live without me & she needed me. So then we get back in the groove of things for a week. Everything was good but my feeling came back hard. So i asked her out again but got same answer. I tried to tell her that i could no longer be friends & forreal this time. But she was begging me to not do it & that she needed me. But i knew it wasnt the way i needed her. I stuck firm with my desicion. Havent talked to her in 3 years. But yesterday she hmu on instagram and told me she missed me and to call her. Idk what to do. My feelings have sloely creeped back again as i think about it and as much as i want to i know in the end it will most likley be the same outcome, but since my desicion. Altho ive been with other women. It just isnt the same & i have been broken since. Never truly got rid of my feelings just pushed em down. She hasnt dated anyone sonce her last bf. Ive had a few chiks but nothing super serious. 1 i would like advice on what i should do and mainly from females whats going on in her head & why is she doing this & playing these games.