Why is my ex still trying to hurt me?

I have an ex girlfriend who I still love, but I hurt her very badly and we were on and off until she broke up with me for good about a year ago. Long story, we fought a lot during the break up, she would try to make me jealous, then she would say she wishes she could hurt me just as bad as I hurt her. She ended up coming back in my life by the end of last year and claimed she forgave me but wouldn't forget and then said she isn't interested in another relationship with me because the first was based on a lie… She threw my past of what I did to her back in my face, so if she isn't interested then why is she still trying to hurt me? I mean she's the one that asked me to help her so she could get back on her feet, so I did. She got mad at me over a screenshot, had to prove I was innocent and then has her friends block me, they hate me and she tried getting my attention the day after she got mad for the screenshot by unblocking me on Instagram to tag me in a comment I made on her friends photos and blocked me back. (All I put were heart eye emojis on her friends photos for those who have an iPhone) then she got mad at me, she said "Love how you follow all my friends, stupid. Like stop stalking.) and I don't talk to any of her friends, I know them so I follow them. So I don't get it. It's like she's punishing me and teaching me a very and extremely hard lesson.

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