[@Akayaofthemoon]Well, gems are hard light, and as we know, they can change their form at will. It possible that she could have always been Rose's pearl, but it's just as likely that she couldn't be. Pearl's defection could have been on homeworld, where white diamond, who I assume is the head of them, resides or resided, and the change to Pearl's space suit would have been to further support her defection from WD. 

But, nothing is really concrete right now, so anything is possible.