Can you provide a summary of Enchantress from the Stars by Sylvia Engdahl?
Elana has grown up in a futuristic, space-age society that is highly advanced and peacful. It is the "government," so to speak, to younger civilizations who are still developing. Generally, Elana's society does not interfere in the workings of other civilizations, but in one case, they have to do so in order to ward off an attack.
Wanting to be involved in ths mission, Elana hides on board the ship headed to Andrecia. She befriends Georyn, who wants to be the hero in this quest and to defend his planet from invasion at any cost. Without revelaing her true identity, Elena uses her telepathic powers to help him do so, but tells him that ultimately, all his power must come from his own choices.
Elana must also work with Jarel, whose job it is to carry out the intervention plan. He must come to terms with what he actually believes is the best thing for the developing civilization and the risks he may be taking in helping Goeryn and Elana.
Ultimately, the characters learn that there is no guaranteed way to secure the success of a society. Men will make their own mistakes and are forced to bear the consequences.