Pink Diamond Theory

Look how cute Pearl is, she made an outfit with a little pink diamond. But this has more significance than it seems.

We know Peridot and Jasper are both subordinates of the gem Yellow Diamond which is why they have a yellow diamond pattern

Similarily, Lapis Lazuli has a blue diamond on her outfit, implying she is or was subordinate to another gem, Blue Diamond

The Crystal Gems on Earth on the other hand, including Pearl, wear stars on their outfits, not a diamond.

But in this particular episode, Pearl wasn’t with the Crystal Gems, she planned on going to space

Pearl was going outside of the solar system (or at least she hoped to). She was hoping to meet other gems, and thus used a diamond to identify her allegiance, to the Crystal Gems, to Rose Quartz.

So my theory is: Rose Quartz is not Rose Quartz at all, she is in fact Pink Diamond, and as her confidant, Pearl would have known her secret.