Hi!
I've been there too. It's hard to end a relationship and it's ok to have her on your mind for a while after you broke up, especially if you had a strong connection or you've been together for a long time. You can't just erase her, you were used to thinking about her all the time.
Also it might be a sign that you need to get better closure and I know a great way to do that. You write a feelings letter addressed to her. And you just let your feelings out and you go: I'm angry/upset about...,I'm sad/dissapointed about, I'm scared/afraid that... I'm sorry for... I'm ashamed for...I hope/I wish...I understand/I forgive you for....I appreciate/I thank you for...This is an amazing technique I learned from Lauren Gray, a relationship coach! Let out all your feelings, don't edit anything and you'll feel relief. One more thing you can do is send her the last 3 positive parts of the letter but not expecting her to respond or react, just to know that you expressed that to her. Try it out and see how it feels.
I hope you'll soon be able to focus more on yourself, enjoy being single and find a new hobby or passion or work on your personal development! Good luck !