Books like Enchantress from the Stars

Elana is a member of a supremely advanced interstellar civilization, on a mission to the medieval planet Andrecia. To her shock, she becomes the key to a dangerous plan to turn back an invasion by an aggressive, space-faring "Youngling" species. How can she possibly help the Andrecians, who still believe in magic and superstition, without revealing her alien powers?Apprentice Medical Officer Jarel knows that the Imperial Exploration Corps doesn't consider the Andrecians to be human, and he has seen the atrocious treatment the natives get from his people. How can Jarel make a difference, when he alone regrets the destruction his people bring?Georyn, son of an Andrecian woodcutter, knows only that there is a dragon on the other side of the enchanted forest, and he is prepared to do whatever it takes to defeat it. To him, Elana is the Enchantress from the Stars who has come to test him, to prove his is worthy....