Agent23
"Honey!!! Wheres my Supersuit?"
Well that and the fact that the earth gods are noted as being far stringer than average. To which i will concede she is also one of the strongest of our initial seven.The underworlds were made/shaped by the mortal souls mostly. She didnt create as much as provide the initial spark for them to do alot of it on their own. Sure she has control over it but shes more doing her job throught instinct of the time for death. The life part is actually more shes just throwing that spark there to welcome a life to the world, rather than creating a soul entirely.
So sure maybe the Siblings thinks she creates/owns souls but truth is actually diffrent, but that would maybe come out if they find out more about how she views them.
So maybe what sets her apart from the other Death gods is how she handles stuff/works.