This is probably one of my favourite scenes from the show. Ever. It tells us so much of the way the Diamonds interact with one another and how they interact with the gems around them.
When BD is rearing towards Steven, Yellow Diamond knows exactly what’s coming. She knows she’s about to be hit with a wave of Blue’s sadness.
Her eyes widen and she leans but doesn’t get up because she knows she can’t outrun it (without looking like a fool at that).
Instead, she braces herself so that she can maintain her composure even as the tears come out.
And she never tells BD to stop crying. She lets the latter keep at it. That says a lot about the YD we know, who is running ragged because she lets Blue mourn while she works to pick up the slack for Blue and Pink Diamond.
It’s interesting too that Yellow Pearl and Blue Pearl aren’t caught unaware by the wave of Blue hitting them. Rather than express shock, they’re trying to maintain their composure as well.
They’ve likely seen this before and have experienced it as well.
Blue Pearl more than Yellow, which might be why she can hold it together a little better.
Even the Zircons below don’t express surprise the way Steven did when BD’s tears first started coming out of his eyes. At the same time, they’ve sobered up and we’re left without the taunting and face-making from earlier in the episode. This means they’ve either heard rumours of or witnessed this in the past.
What I do want to point out is the reverberating sound that comes when Blue cries. That unique ding is probably what induced the crying and Lars is unaffected by it.
That must mean that Blue’s powers, and similar gem abilities work with the use of sound waves that affect other gems via their gemstones or light bodies.