I still need to make edit the edits I am making along with making your oc and Dick Grayson so that's gonna be fun yay- anyways I have two scenarios in my mind for this

1: (they are together)
It was a peaceful day at Waynes mansion and all of the bat's family kids where fast asleep. The only ones awake was Libby, Bruce, Dick, Pandora and Alfred as he was making sure everything was in check. Harley ended up starting her own bakery and lives in a nice apartment in the nice part of Gotham city. It was a lazy day for the large family since it didn't seem any crime was to happen anytime soon

2:
Libby and Pandora are on a mission around midnight and didn't tell any of the bat family so they through that they got taken when they where sleeping and go on a mini hunt to find the girls only to find them sitting on a roof watching the city closely or something like that-