One thing - William, while the Forest Queen has given hom the form of a fawn during the day, is a man, or at least was born human. He says:
"You delivered me from danger then" (i.e. when he was sent adrift like baby Moses),
and so when he says
"Swore to save me from the world of men"
he means she gave him an escape from the cruel world by taking him as her son rather than letting him die on the river, not that she protected him (her natural son) from the human world. The fact that he's her adopted son that she's gone out of her way to save is what motivates her anger at how her love was "repaid".
One thing - William, while the Forest Queen has given hom the form of a fawn during the day, is a man, or at least was born human. He says: "You delivered me from danger then" (i.e. when he was sent adrift like baby Moses),
and so when he says "Swore to save me from the world of men"
he means she gave him an escape from the cruel world by taking him as her son rather than letting him die on the river, not that she protected him (her natural son) from the human world. The fact that he's her adopted son that she's gone out of her way to save is what motivates her anger at how her love was "repaid".