As koo explained, something triggers the movie-like brainwashing, everytime Pearl wants to talk about WD/PD it is triggered and something makes her cover her mouth, in this example

I will say it again, i really thought Pearl was just messing with Steven xD, but that theory about mind control is interesting

That last part is also likely, it could be just a trauma, Pearl's former owner being abusive is something that kinda fits

Do you suppose she wanted to tell Steven the truth of shattering at the time?  I also believe that there is Diamond involvement in PD's shattering, but I'd be surprised if Pearl knew this, and not Garnet.

I wonder what it was she was trying to reveal.  The lead up makes it seem like she was going to reveal something about the Diamonds, maybe that she belonged to White Diamond and/or Pink Diamond.  I'm not sure that detail in particular would fall under attorney-client privilege, since the "client's" identity isn't really a secret.  Also, wouldn't it terminate after shatter, at least in the case of Pink Diamond?

Okay, I think both of them are still fair game at this point, since I can't recall an instance where PD's name was stated outright by Pearl.

I'm not sure about Garnet, since Ruby might not've been a WD Gem.  WD making an entrance would be pretty cool, because at this point every other Diamond was introduced verbally before appearing in person.

Wouldn't it be dangerous for other Gems, especially lesser ones, to know that this occurs?  If Garnet and possibly Peridot are aware of this information, why haven't they disclosed this fact already?  Steven's pressed Pearl for answers on several occassions, and Garnet should've been frank with him if Pearl is contractually bound to withold what she knows.

I don't know, this just feels way to convenient for me; interesting concept, but contrived.

We need to look at it in two ways. Either Pearl was conditioned by someone else or she conditioned herself. It's not far-fetched of an idea that someone subconsciously represses their memories due to the high levels of stress or a form of post-traumatic experience brought along with it.

And it also plays along the notion brought up by Garnet that Pearl's sensitive to this kind of stuff. Garnet and the rest of the CGs knows that Pearl will not and cannot say the memories she has.

If it was just conditioning to repress memories by someone else, Pearl's problem would just be the inability to convey what she remembers or the inability to remember it. When Pearl was trying to tell Steven, you can see she is very distraught. As if the idea of bringing up such memories is painful for her.

“

So, Homeworld... I always hoped you'd see it some day, but I thought I'd be there with you. Being taken there as a prisoner, I suppose it was something of a dramatic experience. It's just, [Sits down] Steven, I'm sure you have a lot of questions you'd like answers to, like about the Diamonds, for instance. There are things that are impossible for me to explain. But I want to. I -- [Covers her mouth for a moment] Steven, I -- [Covers mouth again and doubles over]

”

There's also the idea of Pearl having been through some sort of Pavlovian/Classical conditioning but I really don't see why they [Homeworld] would.

I think the latter (Pearl conditioned herself) is better supported by canon at this time.  I also think repression/suppression could apply to BD, but that's a different tangent (How do you strikethough text?  I've wanted to use that feature for the longest time).  This options has the potential for satisfying character development for Pearl if she ever learns to confront her tendencies and "face her fears".  Maybe Rose couldn't get through to her on this issue.   Maybe Rose is in part, the source of this issue, as we know how anxious Pearl became when Steven found out Rose shattered PD.

Classical conditioning: that's an interesting way to think about it.  I'd imagined that Gems in general were "conditioned" a la Aldous Huxley's Brave New World to reinforce class differences.

Yeah, that path makes more sense

That is a possibility we should consider, but I would rank outside conditioning as more likely then self conditioning, we know Gem society is capitol T totoliarian so this just feels more consistent with the show so far.  Subconcious suppression would require Pearl to not even be aware she HAS information, but she knows that she knows and approatches Steven with intent to use that information to help him despite her limitation in conveying it.

Under that interpretation Pearls 'sensitivity' is a byproduct of conditioning, which is consistent with the 'clockwork orange' stuff they may have done to her to achive the state, trying to convey this information is 'triggering' her so to speak.

Subconcious supression both applies to outside and self conditioning, what applies to one, applies to the other, the main difference between the two is who did it and why it was done. Self conditioning is usually done by the self to preserve mental health, more of a defence mechanism. Outside conditioning is usually done to make the person forget or prevent

Also, subconcious supression doesn't necessarily mean complete lack of supressed memory, rather the brain refuses to acknowledge that the memory exists. This is what often leads people to become distraught, the concious mind tries to remember but the unconcious self is fighting to keep it from surfacing. Which leads to an in-fighting with the self.

Certainly can't argue with that.  

And now I understand the trigger!

Here's a creepy thought: what if, outside the "mass corruption", White Diamond had nothing to do with anything Earth-related?  What if her role in the Diamond Authority and Gem Society at large isn't much more than an oracle of sorts, and she has in fact taken a back seat to the other Diamonds?  I don't necessarily mean she's clairvoyant, but rather a source of wisdom.

I wonder what kind of leader she is/was to Gems in her court.

So, WD moves the strings? i like that, makes sense too

What if Pearl covers her mouth because PD really made her suffer when she was her diamond, to the point that she is beyond the Lapis Lazuli scale of trauma?

Not my headcanon about PD, but it fits

Edit: NOPE NOPE AND NOPE, but PD kinda silenced pearl in a way :v