What i think is happening is that she is trying to get her father to notice her, hoping he will come back to live to punish her for making a big mess by pooing or something like that... I don't know japanese though, so i don't really know. :P
Is there vomit? i mean i do see the bean paste of the parent but clearly that wasn't vomited, you kinda see the blatlantly obvious gashes in it's body and stuff.
And while the action may be meant to "wake up" dad, that doesn't really make them any less, retarded, in usual dramatic stuff they would go "remember that promise of going to the park" or "You said you would make my own easy place when i married a nice yukkuri ;_;", etc.
Of all the methods she choose to try to have a reaction from the apparently dead dad, she choose the most stupid one.
Hmm now that i think about it, i would say this is more dumbass than retard, at least without the translation confirming that she may had done that without EVEN realizing her pop's situation completely, but i honestly doubt she's that obvious of what happened to it >_> . . . i hope . . .
It seems that Kiriraitaa skillfully avoided all of our predictions: no puke, no death from fear,no attack, no piss, no scream, no true happyness. She just takes a skillful dump on herself while smiling.