I frend zone a girl i like cause of a other boy

I like this girl who is 21 and I am 23 but I have friend zone her due to her other friend who is 15 and has a massive crush on her but as soon I try to get close to her he basically makes mine and her life miserable I do really like her but the boy always gets in the way and iv been arguing with him about it I don't no what to do because I do really like her
and advice guy would be good