I'm 100% sure that I'm gay but I have feelings for a girl?

This might turn into a long ramble, but here goes nothing.

One summer I met my best friend, let's call her K. K and I we grew incredibly close; at that time, I was closeted and in denial about being gay. Pretty much, I saw her as the girl that woud help me "get over" being gay. (Oh how foolish I was. Guys are too attractive for that.) So around December, I asked her to go out on a date with me which she happily said yes to. After a good movie date, I took her out to the pier and when I was about to go for a kiss I stopped myself. Something didn't feel right. (Since I'm gay obviously lol) After that, I told her we couldn't work and then we had a big long awkward gap where we didn't talk. Fast foward to the next summer after coming out to a whole lot of people at my school and also a break up with my first boyfriend(Was all closeted though my close friends know of it. Including her.), I started to talk to her again and our friendship rekindled. I came out to her and we became best friends. We talked and hung out a lot, the typical best friend stuff, but only as best friends.

Fast foward again to a few weeks ago, which was her sweet 16. K and I had a very heart-to-heart moment when we slow danced to one of our favorite songs, Chasing Cars by Snow Patrol(Has a lot of meaning to us), and I realized that a part of me wants to be in a relationship with her. Here's the major problems with that though:

1. I'm 100% gay, I feel no sexual attraction to her physically at all even though she is beautiful. It's more her personality and who she is on the inside.
2. She has a boyfriend and has pretty much moved on from what we had at one point. Liking her will only lead to problems.

Am I just in a rut because I haven't found any guys? I shouldn't be wanting a relationship wth her so bad, I don't have any physical attraction to her. This is all so confusing. Help appreciated.

TL;DR: Liked a girl when I was in the closet. Almost dated. Stopped myself because I knew I was gay. Became her best friend after a long awkward gap of not talking. Had a heart-to-heart moment with her at her sweet 16 a few weeks ago. Can't get over her now. Don't like her physically but her personality is so endearing. Not sure what to do from here because I'm 100% sure I'm gay.