THEORY 1
I think 8 year olds might not know how to create e-mails (you need more e-mails to create more accounts). This kid is plain retarded and shouldn't be here but I don't think that's the downvote fairy.
THEORY 2
She might have used her mother's other e-mails to create other accounts.
THEORY 3
I don't think this kid would downvote everybody's memes just because she hated on you.