Lian needs her daddy. Considering the rate she loses potential playmates and relatives, as well as the way she blows through babysitters & nannies, she needs a constant in her life. (Currently childsized contemporaries: Jai and Iris. Dead, adopted, disappeared or magically aged contemporaries: Robert & Jennifer Long, Cerdian, Robert Queen, Sin, her half brother, Chris Kent, Helena Kyle, Baby Brown... off the top of my head)
And can't see DC managing to deal with Lian living with Dinah gracefully, especially considering Lian's amazing ability not to appear in an Arrow Family Book, despite having been a family member longer than both Connor and Mia.