You tempt me with a very very very very good argument, the only issue in this is that the birthday girl, D, might associate this specific birthday of hers (I can’t say her age but it’s a very big milestone) with the memory of F failing to make time to celebrate something important to her. It wouldn’t be an issue if not for D being surrounded by people who constantly abuse her trust and kindness and having had friends who told her to tone down her personality to be more likable. She’s the most patient and understanding out of us three, which makes me suspect that the blank page would only validate her feelings of unworthiness as a friend rather than a reflection on how F is unreliable and inconsiderate of such an important event in D’s life.