Each of the Diamonds we’ve seen never actually realized what the mistakes they made with Pink Diamond were.
Blue doesn’t regret not listening to Pink’s pleas to stop the colonization; She still believes the Zoo was a pretty good idea, and that Pink thought so.
Yellow doesn’t regret being too hard on Pink; She regrets “giving in” to Pink’s desires.
They mourn for Pink, yes, but they don’t mourn Pink Diamond the person, but rather the idea of who they thought she was.
You could argue that this is all because they didn’t know of her alter ego, which is true (it’s hard to really know someone when they’re much more comfortable faking their own death and continuing on as another person) but at the same time I don’t think the Diamonds actually want to analyze how they wronged Pink.
They’re more comfortable mourning her in a way that refuses to acknowledge how they drove Pink away, and would rather place all the blame on “Rose Quartz” and the Rebellion and Earth.
Their guilt seeps through of course, but ultimately Pink’s Pearl (the Homeworld equivalent of Siri) and a down-on-his-luck human musician ended up knowing the “real” Pink more than they ever did.
This question is kind of hard, so maybe it’s a little different from what you mean.
God I wish my English is good enough to express what I want to say. Next time somebody just give me the dialogue that I can fill in.(I’m kidding that’s too lazy)