Ex Crush annoying behaviour!!?

Anonymous
May be my question should more like this, "HELP ME OUT TO PUNCH ON HER".
Am mad at my ex crush ( girl ) over a month coz of her stupid attitude towards to me. Last year i had a crush on this girl (classmate). One day i told her how i felt but she rejected it, coz am from diff religion. But i made a huge mistake of being clingy to her there after which regret it later. Then she got a new bf and told me not to disturb anymore. I was heartbroken. But i respected her decision and let her go. Then the problem arised. She starts to stare at me everyday in the classroom and act differently around me and posting some sad status and songs that she was missing someone blah blah. Then i finally found her bf is many miles from our place and they can meet only after 3 years. I felt like she is trying to using me and started to ignore her. But the more i ignore the more she bumping into me. Am clear that i don't need her anymore in my life.
Can any tell me how to tell her that i was interested to be second option. Either polite or mean way. I can't live like this anymore.
Ex Crush annoying behaviour!!?
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