I understand kids do crazy shit, show each other their private parts and a host of other shit we wouldn't condone. But usually there's some consent involved: I show you mine, you show me yours. She literally opened up her 1yo sister's vagina walls. And tells the story as if it's a gag, oblivious to the fact that her sister...probably doesn't want something like that discussed.
And if we go even further down the derp hole, how can you talk about "agency" while denying your sister any? Even if we excuse the diddling as kid shit, discussing it today without her approval violates her privacy/agency/etc etc right?