So we've seen Blue Diamond and her pearl and Yellow Diamond and her Pearl. The pearl's appearances resembles theirs of their diamond. White Diamond's gem is on her forehead, and so is our Pearl's. I support the theory that Pearl belonged to White Diamond. But why does she have the pink diamond symbol on her space suit? Here's what I think:
Pearl belonged to White Diamond. White Diamond came to Earth to check on Pink Diamond or something. Whatever went down, Pearl would've crossed paths with Rose at some point. Later on Rose pulled Pearl away from White Diamond. Rose, being all loving and such, made Pearl her pearl. Pearl would probably have adopted the Pink Diamond symbol because she'd be under Pink Diamond's court. Later Rose and Pearl rebelled, starting the Crystal Gems.
Hope my theory made sense.