The Forgotten Weasley

Sapphire is the forgotten Weasley, born 5 minuted after Ginny, she is the second girl in the family. But her family always forgets she's there. She lives in the extra closet in the attic where there she has to live with whatever temperature it outside. She eats the scraps from dinner so she eats very little. She is remembered by her family for the first time in 11 years when she gets her Hogwarts letter, Then she is forgotten again until the next year when her letter comes. But what if one year she gets fed up and leaves?