Character by Rebecca Sugar. Minor spoilers for Cartoon Network's "Steven Universe".
Homeworld is a planet inhabited by the alien race known as Gems, which use data and energy stored in their Gemstones to create avatars out of light that make them capable of interacting with their surroundings. The Gems of Homeworld are interplanetary colonizers that adhere to a strict caste system based on gemstone type, with the Diamond Authority at the top.
Pearls are low in the heirarchy, created to be servents that follow every whim of their high ranking masters. Our Pearl was created for Pink Diamond, the youngest and most inexperienced of the Diamond Authority. Pearl accidentally encouraged her Diamond to explore Earth, which was meant to be Pink's first colony.
Pearl always remained by Pink Diamond's side, even when Pink Diamond started a rebellion in defense of Earth under the alias "Rose Quartz". The small rebellion grew into a full scale war that lasted 5,000 years, during which Pearl trained herself to fight to protect Pink Diamond. To end the war, Pearl agreed to help fake Pink Diamond's Death so she may live only as Rose. Her last order to Pearl was to never speak of this event.
Years after the war, Pearl and Rose are close as ever. Pearl makes it apparent to those she comes across that she believes that despite Rose's many past human lovers, no one will ever be as close to her as she is. This crumbles before her as Rose falls in love with Greg Universe, knowingly choosing to die in order to birth her son, Steven.
Post Rose's death, Pearl is left feeling devistated and confused. Everything she did, she did for Rose's sake and now that she's gone, she feels she is worthless without Rose, despite Rose encouraging her to be her own person. She becomes prone to lashing out at her teammates when Rose is mentioned and is hostile to Greg and his attempts to get along with her. Her co-dependent mindset was nearly projected on to her impressionable swordmanship apprentice.
With the aid of her friends, Pearl starts learning how to let go of the past and exploring her own interests. Through an open discussion prompted by Steven, she admits to Greg that she never hated him, but was upset at Rose's choice. Her teammate, Amethyst, also encourages her to interact with humans. Pearl's other teammate, Garnet, tells her that only Pearl can decide what she can be.
Pink Diamond's order to Pearl to never speak of what she knew wasn't something Pearl followed through on, but something she was physically forced to do, even against her own will, as Pink's made-to-be servant. With his magical powers, Steven goes through her memories, discovering what happened for himself. This act finally breaks her seal, allowing Pearl to finally be free and truly to do and be what she wants.