How to make my crush friend fall for me when she knows I like her?

I am a 22 years boy and I have a crush on my friend whom I never met physically after my 5th grade and now I am about to graduate. I started talking to her 2-3 years back and after 3-4 months talking to her I started falling for her even I didn't meet her. I told her but she said she don't feel the same way. I minimized contacting her and afterwards in 3 years I told her again 2 times that how I feel about her and wants to marry her but her reply was same that she don't want relationships. She is still my friend. I started talking to her again she she talks the same way she talks earlier but some times she behave very weird and sometimes very sweet. I asked her to meet me 2-3 times but she said she will meet when she would have time. Now I want to have my last proposal for her. I don't know what to do.

How to make my crush friend fall for me when she knows I like her?
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