Light of the Gods

From fictiondb:

1860. At her rich, look-alike cousin's pleading, impoverished Sacha Waverley undertakes a daring masquerade. She travels to Scotland posing as Lady Deirdre to care for her cousin's fiancé, the handsome, wealthy Duke of Silchester who has been temporarily blinded in a hunting accident. It's Sacha's one chance to wear fine gowns and be waited upon--a fairy-tale come true. Then the unthinkable happens... she loses her heart forever to a man she can never have.