Okay. So to start, in Mirror Gem, Pearl summons Lapis's mirror, thinking that it's simply a tool. It would seem that none of the Gems knew that Lapis was in the mirror, but there is evidence that Garnet and Amethyst knew, and they kept it a secret from Pearl EVIDENCE 1. Garnet and Amethyst probably gave the mirror to Pearl because they knew that she would see it as a tool, nothing more. 2. When Pearl says that the mirror shouldn't be speaking to Steven, she covers her mouth with a look of horror... As if she were realizing what the mirror really was. 3. When Amethyst says, "Garnet, do something," her and Garnet are NOT looking at Steven. They're looking at Pearl as she realizes what the mirror is. 4. When Lapis says "You three," the viewers probably think she is talking about Garnet, Amethyst, and Pearl. But in the episode "The Answer," Lapis is seen on Earth at the time that Ruby and Sapphire fused. So when Lapis says "you three," she may be talking about Ruby, Sapphire, and Amethyst, which may explain why Lapis first attacks Garnet.