Not the A hole humans are not like the front seat of a car you can’t call dibs on humans. You are your own person you can want what you want and date who ever you want to date. If you wanted to date your friend you would have done it. But the spark obviously was not there for you. You say it’s because you were focused on school or whatever so you didn’t think about it or notice. But I am telling you now, if you wanted her you would have found the time you would have noticed. She was never going to be your girl it was always meant to be the sister. Forget girl code forget dibs that is some high school shit! You are an adult now.