I was vague there so I'll clarify!

Lyn's dad is a goblin and he has self-loathing issues. He would rather not be reminded that he is a gross creature and uses magic to disguise him and his daughter as humans. Though he would like to permanently become human if at all possible. He hires a caretaker for Lyn who happens to be knowledgeable in some magic so he takes advantage of the opportunity.

The magic has some bad side effects for Lyn though because her dad used magic to disguise her right from birth so she has recurring nightmares about being a monster of sorts that goes unresolved. At least until Lyn's caretaker notices that something's wrong and does something about it.