Mrs Fotheringill is Daisy and Poppy's teacher. She's a push over and is slightly scared of naughty children. She is American and doesn't seem to be either elf, fairy or any other magical creature. She can be a shrunk 'big person'.
She disappears and her shoes are left over. There is a theory that she was a fully grown adult but saw the little kingdom and king thistle shrunk her and forbid her to go back to her normal life. So she decided to be the teacher.