Lemme tell you what I did
I avoided the person I liked
I mean, just break off the friendship altogether because it's hurting you so much. You're so distracted by this girl that you're not even doing things for yourself. Time does wonders
It might take a little longer for you, but it took me a year, I forced myself to delete Twitter and instagram so I would be less prone to stalking their social media. I also deactivated my Facebook. Kept myself busy with my studies and own hobbies. Made new friends. Tried new things. Kept away from things that reminded me of them.
You'll still remember them for probably the rest of your life, maybe still have a little feeling for them but you'll look back at it one day and just smile. You'll find love in the near future who'll cherish you and love you back. Just wait a little. You're so focused on this one girl, you're failing to see the world, and all these other potentially more suitable girls.
It calls for drastic measures. Cut all ties with her, change phone number, email etc. Sure it'll hurt for a week/month or so but you'll get over her. There's no one in the world who you can't get over.
And I'm speaking from experience. I liked this guy for about 6 months then he got this super hot, younger girlfriend. I still liked him for ages before I decided to get myself together and actively made myself get over him. He wasn't worth me wasting my time if he never saw the good in me, and there was never a chance for me anyways because he really liked his gf.