I am in no way diagreeing with those who think Rose Quartz is Pink Diamond. Cause then this might happen.
First up, as we all know, the Diamonds are HUGE beings. I mean look at Yellow Diamond, her Pearl is the size of her foot. HER FOOT PEOPLE! And now look at Rose. You see what I mean? And secondly, from what Peridot said in Too Far, she said that Quartz are as of a warrior class, like Jasper and Amethyst. So maybe Rose was a warrior for Pink Diamond who then betrayed her, then Pink Diamond was expelled from the Diamond Authority for her misbehaving Warrior. Lastly, during It Could've Been Great, we see murals of all the diamonds. All except Pink Diamond. Now as the murals are being shown, Pearl is no where to be found, which has led us to believe she was looking at Pink Diamond's mural, which may or may not be Rose. But after all, that's just my theory. What do you guys think?