Pearl did cross my mind briefly, to be honest, but I wasn't too sure of it personally.
Well there's certainly a
lot of evidence pointing towards Pearl. For one thing, look at her reaction to when Steven first hears that Rose shattered Pink Diamond,
And here when Steven brings the topic up again,
Her reaction is much stronger than that of any of the other Crystal Gems. Now, there are a few alternative explanations as to why her reaction is so strong -- Amethyst probably hadn't emerged yet when Pink Diamond was shattered and so it's unlikely that she has very strong feelings about the event, and it's debatable whether or not Pink had been shattered yet by the time Garnet joined the rebellion (also, Garnet usually maintains more of a stoic appearance anyway). Also, out of all the Crystal Gems, Pearl was the closest to Rose -- so if we assume that Pearl at least believes that Rose did it, then it makes sense that she'd be the most distressed about Steven finding out.
BUT, these two screenshots in particular have been used
a lot to suggest that Pearl is guilty and perhaps hiding something, and it's not hard to see why.
Also, I think it's safe to assume that whoever shattered Pink, was shapeshifted to look like a Rose Quartz when they did it. After all, the only confirmed eye witness of the event is Eyeball, and we've already seen that she can be rather easily deceived by gems shapeshifting to look like other gems (as was the case with Amethyst posing as Jasper). Now, unlike the other Crystal Gems, we've never seen Pearl shapeshift. For a long time, the predominant theory amongst the fandom was that she was defective in some way -- but all of these "Pearl is defective" theories existed before it was known what the role of Pearl gems actually is, and said theories mostly cleared up shortly after. Knowing that Pearls are mere servant gems, it's possible that they simply aren't designed to be able to shapeshift. After all, why would a mere Pearl
need such an ability?
BUT, when the topic of shapeshifting was first addressed way way back in Cat Fingers, Pearl's exact wording was that
all gems can shapeshift. Additionally, the other Crystal Gems (or at the very least, Amethyst) believe(s) that Pearl is capable of shapeshifting, as Amethyst told Pearl to shapeshift in Secret Team. And even if Pearl did want to keep her hypothetical inability to shapeshift a secret from Steven, I have no idea why she would also want to keep that a secret from the other Crystal Gems (not to mention, it's unlikely she'd even be
able to keep such a secret over the thousands of years that she's known the other Crystal Gems. The truth would have to come out at some point). With all of this in mind, the theory that I've now seen floating around is that the reason why Pearl doesn't shapeshift, is because of a traumatic event from her past that involved shapeshifting -- for example, shattering Pink Diamond.
There's also what Zircon said during the trial:
So how did a Rose Quartz, with no business being anywhere near Pink Diamond, get so close to her in the first place? Where were Pink Diamond's attendants, her Agates, her Sapphires? And where was her Pearl?
Many have speculated that the writers ended with that statement for a reason -- suggesting that the Pearl we know was perhaps Pink Diamond's Pearl, and that she committed the act. Not only would Pink's Pearl certainly be able to get close to her, but also -- who would even expect
a Pearl to do such a thing?
Additionally, Pearl's space suit has a Pink Diamond insignia on it:
Which also supports the theory that our Pearl was Pink Diamond's Pearl. The only problem with this is that it raises the question: why is our Pearl white, rather than pink? After all, Yellow and Blue Diamond both have Pearls that match their respective colors, and it's not like pink pearls don't exist in real life. So Pink Diamond's Pearl most likely would have been pink, as well.
Another thing to note about Pearl: she's emotional, and she's done some stupid things when her emotions got the better of her. Things that she knew was wrong, and that she later regretted -- like when she posed as Peridot and repeatedly re-built the communication tower in order to continuously fuse with Garnet and become Sardonyx. And on the topic of Pearl being emotional: in Friend Ship, Pearl, in an attempt to make up for deceiving Garnet during the whole Sardonyx incident,
frantically goes after Peridot -- throwing herself at Peridot's holograms in a desperate attempt to catch Peridot and please Garnet. It's quite clear that her emotions are getting to her, as she's normally a lot more tactical and strategic with her fighting, and her actions in the first half of the episode are anything but tactical. Most notably, however, there is one point in the episode where she attacks one of Peridot's holograms and quite clearly
aims for the gem. Pearls spear touches holo-Peri's gem right as it disappears.
Pearl believed that was the real Peridot -- and if it was the real Peridot, then Pearl could've very well shattered her. Granted, she did it in a fit of rage, and she certainly might have regretted it later. But the point remains, she could've done it.
It's possible that she could have shattered Pink Diamond in a similar fit of rage.
Also, whoever shattered Pink Diamond, did it with a sword, and we know that Pearl's pretty good with a sword.
Lastly, as for the whole, "in real life, only a diamond can break another diamond" thing? That's actually not completely true. In real life, only a diamond can
scratch another diamond. But as for shattering one?
Just about any rock-shattering object will do, so long as you apply enough force.
Yellow and Blue both show actual grief when it was just the two of them.
To be honest, Yellow Diamond's grief never seemed very genuine to me. I think it's very possible that Yellow's expressions of grief were all just an act put on for Blue. And even then, Yellow looks like she just wants Blue to get over Pink's death already, and she honestly even comes across as a tad pushy about it.
Now, one could argue that Blue
has been grieving for a ridiculously long amount of time, so it makes sense that Yellow would want her to move on already. But gems don't die from aging -- only shattering -- and no Diamond has ever been shattered other than Pink (that we know of), so it makes sense that grief would be a rather foreign concept to the Diamonds, and so it's unsurprising to me that Blue would be grieving for so long and that she would be unable to move on. I think it's more surprising that Yellow
isn't endlessly grieving in much the same way.
Also, during the trial, Yellow seemed to be very eager to wrap things up sooner rather than later. Blue kept insisting that they give "Rose" a chance to speak, but Yellow seemed perfectly content skipping right past that -- and if we assume that she is guilty, then it makes perfect sense that she'd want to see Rose condemned before any evidence can be brought up to prove Rose innocent.
Lastly, her reaction to Zircon's accusations -- some have argued that her outrage isn't an admission of guilt as much as it is simply her being appalled that Zircon would suggest such a thing. After all, we've seen before that Yellow can be short-tempered, like when Peridot called her a clod. However, I think it's worth noting that
Yellow doesn't look particularly shocked when Zircon accuses her. To me, she seemed to be surprisingly calm at first -- as if she was trying to downplay her reaction in order to avoid looking guilty (...and
then she poofed Zircon and sent the robonoids after Steven and Lars). By comparison, she was
much more visibly outraged when Peridot called her a clod (and most likely would've poofed Peridot -- or perhaps even shattered her -- if they were interacting in-person). So I think that, if Yellow was innocent and
truly caught off-guard by Zircon's accusation (and allowing herself to react naturally as opposed to holding back), then she would've had a much stronger immediate reaction.
