A girl or boy with blonde hair who has no memory/ easily forget things the phrase that would be used id memory like a goldfish, but seeing as she / he is also blonde and has blonde moments, but also forgetting things the term blondefish is used to describe them forgetting and not knowing simple things.
Jess says: I told you that a second ago
Amelia replied: oh ye I forgot I’m just having a blondefish moment
1) A common form of dementia, a neurologic disease characterized by absence of mental ability severe enough to interfere with normal activities of daily living, lasting at least six months, often present from birth. Blondehiemers frequently occurs in teenage girls, and is marked by a severely limited cognitive functions such as remembering, reasoning, and planning.
Hannah's Blondehiemers is so severe she often not only doesn't get jokes, but doesn't know when a joke has been made.