@JBBJSBB you did, but I'm gotta speak up for
@alfirizkyr anyway. Whodunnit, Whydunnit and Howdunnit all have established spellings in English. I don't know if anyone lists them as legit words, but mystery lit types spell them that way.
And I'm on board with the 'it's her mom' theory. Especially if the mother died while she's an infant. Patting a baby's ass is often used as a means to calm them.
For non mystery types, the three standard formats of mystery stories are:
Whodunnit -> the mystery is 'who is the perpetrator'?
Whydunnit -> the mystery is 'why did the perp do it'?
Howdunnit -> the mystery is 'we know who did it and why, but how the heck did they pull that amazing crime off?'
And of course, there's police procedurals, but that's something of a different genre.