Logistics. Khandalyce murdered 'some time' after Karlie.
Holdom has been charged with the murder of Karlie. Therefore.. assuming Khandalyce was with Karlie ( and if not, why not? and where? why wouldn't she be? ) then Holdom , after murdering Karlie, ( in front of Khandalyce?) had to take the body to Belanglo and then , like all murderers, and me and you, return to the place he departed from. Where, one assumes, Khandalyce still is .
And then what? If he didn't kill her, he knows who did. If he didn't have the last guardianship ( I use the term loosely ) then who did ? he must know. Is it possible he just left the baby there , wherever there was , in Canberra and walked out alone? I find this scenario a bit fantastical, not impossible, but improbable. .... It requires a complete stranger to be injected into the story, one with murderous intent on a child, also..
Where did he take her? either alive or dead at this point. Who else was with him? or was he alone? ... was there a destination in mind?