How to get over someone?

How to get over someone you can't have? For context, I don't fall in love easily. There have only been a select few women in my life I have felt this way for. She is amazing. Super cute, bubbly, feisty, confident, strong, independent, super goofy. Shes got an adorable laugh and I just love listening to her or being around her. I don't think about her sexually, shes so much more than that. Like I want to earn the right to think about her like that or romantically. We get along great, I feel we match energy. I love to pick on her too, its adorable to me when she slugs me or gives it right back especially when she gets me so good I have no good comeback. But she is spoken for. As far as I can tell her relationship is strong and healthy. Hes a good guy, I've met him but can't help but feel jealous. Can't help but feel she belongs to me so to speak as selfish as that sounds. Part of me wants to see her everyday but its painful, but it is equally painful not seeing her. She's on my mind everyday. I hate this so much.