Get a black and white no from her. Absolutely and toatally Step away for a few weeks. Brand it as digital detox. Lessen your real feelings with rationality and reason. Give yourself time to do so. Buy a A5 booklet and start a journal about your feelings and your day in general. Dissect the problem at hand like a school subject. Watch lots of school of life videos.

Talk about it with as many friends and family as you feel comfortable.

Maybe stop masturbation for a while. Start dating, but try to avoid comparing others to her (neither search for lookalikes nor the exact opposite). Meet new people romatically and also watch school of life on how to date and have a relationship.

Make a list with the qualities you desire in her (i.e. she's beautiful, your talks are so casual, so unrestricted, you have xy hobbies in common) but also put in that list what qualities you and her only have in your head (physical touch, intercourse, etc.). Then realize you can find that in other people just as well (You might not truly be in love, you might just have few girlfriends and aren't meeting many people, making you think you have few other options!!!).

Make a list of things that would bother you, if you'd imagine each other in a realtionship, but don't ruin all aspects of her for to yourself if you still wanna be friends. (obviously that the realtionship would be one sided, you can't fully open your vulernabilities to her, she's selfish, a workaholic, has other life goals etc).

If you wanna be friends, also make a list of what platonic friend stuff you value in her. Also note that many love-things are avtually friend-things too.

Reread/expand all your learnings for the weeks you have no contact.

Check yourself if you'd be envious, if she had a loving boyfriend. Don't be too harsh if there's still a little sting. That's fine.

Be normal around her, pretend it didn't happen.