I feel very strongly that it is impossible for Pearl to have been the one who shattered Pink Diamond. I know it is possible to shatter a diamond without a diamond but I think there has to be some rules. I just don't think she's strong enough or has to capabilities to do something like this. She almost got completely destroyed by sugilite. To me, every time I hear someone say Pearl shattered Pink Diamond I see a gem like ruby shattering a diamond something like that
I understand your apprehension. While she may be skilled, Pearl is by and large the least physically powerful of the crystal gems. Unlike Garnet, Amethyst and Steven she doesn’t have super strength, and unlike Peridot and Lapis she doesn’t have the kind of bending powers that could lift trucks or part seas.
However, you are forgetting one very important thing: whoever killed Pink Diamond made it look like Rose did it.
Now, I’ve said before that I thought Pearl shapeshifted into Rose to do it, which would have given her temporary strength that was at least proportional to her size, but there is another option I haven’t mentioned:
While Pearl may only treat her as a training dummy these days, Holo Pearl is far and away Pearl’s most astounding power. At any time Pearl can conjure as many as five fully physical but disposable copies (maybe more) to fight in her stead. Any of them can fuse with the others to gain extra strength, and it likely that they can take non-pearl forms as well.
How likely are we talking? Well in the game Sword Dancers on the CN website, Connie can fight holo Connies throughout the game
If she can do that, there’s no reason Pearl couldn’t have sent a holo Rose to kill PD without forcing her to get her hands dirty. Eyeball, being so bad at telling colors apart that she mistook an amethyst for a jasper likely wouldn’t have noticed that Rose just happened to be blue