I kinda still like her a lot

Well I (20M) met her (19F) around two years ago, we quickly became friends and soon closer friends. I liked her and thought being in a relationship with her doesn’t sound so bad for both of us. I told her about it in a romantic situation and well….she doesn’t like me back.

We go on back and forth with the whole thing of me not wanting to ruin our friendship and she aswell feeling the same way, so we stayed good friends for a while. I really enjoy talking to her it’s so uplifting to me to the point that I usually call her when I’m down because she never fails to make me feel good. I knew she liked one of our friends (20M) deeply before and that’s why she didn’t want me, but I was always supportive, u know trying to convince myself that I’m already over her and that I’m a good friend. But recently they started actually flirting, and I couldn’t bare it. Last time I was with them I was practically 3rd wheeled. Then we went out with two others and I was absolutely 5th wheeled like to the point where I just left and met them again later. My last decision was to just stop talking to them, get busy with uni and just quit the whole thing. But they’re a few of my closest friends.

I don’t know what to do. There’s a possibility that I still like her but that’s so shit and pathetic IMO. I can’t stand and watch the girl that I really like flirt with someone else let alone my friend but I also don’t want to lose my closest friends. A birthday I coming soon and I will have to travel around two hours to see them (which is what I always do btw) but I’m not sure if I should go. I’m thinking like maybe leaving them together so they could go out on a date or smthn would be better. I really am in a awkward situation.

Tl;Dr!
Well I like her she likes someone else it’s been more than a year I’m supposed to be over it but I’m not and idk what to do.