Gorgeous! I think you do fine job combining her beauty with her toughness. Many depictions of Lúthien make her look rather delicate, but your version looks capable and confident - just the way she's supposed to be.
A great Luthien! I like your style of coloring And the white light in her hands is very good too! It's good that you chose "blue" as a dominant color in this picture; I think it suits this tale very much.