It's a possibility.



Personally, I have three. Yellow did it because, as you said, Pink seemed frivolous, having an interest in humans. Perhaps even, for all we know, she was intending to meet Rose Quartz to peacefully end the war, and Yellow couldn't tolerate that. I imagine if she was responsible, she want's Earth gone the same reason why Blue wants it still there... she wants to forget the whole debacle. And her crying during the song? Guilt, not sorrow.



Second possibility is Yellow did it or was involved in the murder... under orders from White Diamond, who is the real monster here. For reasons similar to above, Pink may have broken the mold and been deemed just as defective as the rest, and those gems who saw what happened were hushed up... or worse... to keep quiet and keep the remaining Gem population under control. So similar to above, just with Yellow further down the pole.



Third, which is quite a stretch I admit, but was presented to me and does hold some interest... our Pearl... the Crystal Gem Pearl... was once Pink Diamond's Pink Pearl... and SHE did it to save Rose Quartz. The reason Rose would take responsibility for such would be to spare her beloved Pearl's reputation and feelings. And the reason Homeworld would allow it, is because they would fear being overthrown by a Pearl rebellion (they all have one, after all) if the Gems knew a mere Pearl could ascend to such. The idea a soldier like Quartz could topple a Diamond is more believable, and less cause for concern. Flimsy but... there is a chance.