Wikipedia
She-Ra is a fictional character and the protagonist of the Filmation cartoon She-Ra: Princess of Power, debuting in 1985. Also, a series of toys under her name were produced by Mattel. She is the alter ego of Princess Adora and the twin sister of Prince Adam/He-Man. She-Ra was intended to appeal to young girls in the same way that He-Man appealed to young boys. Filmation writer Larry DiTillio created the backstory for the property.
She-Ra is introduced in the animated movie The Secret of the Sword as Force Captain Adora, a member of the Evil Horde that rules the planet Etheria. Princess Adora discovers that she is the long lost twin sister of Prince Adam of Eternia, having been kidnapped as a baby by the Horde's leader Hordak. She is granted the Sword of Protection, which parallels He-Man's Sword of Power, gaining the power to transform into She-Ra, her secret identity.