Originally Posted by
Restingvoice
I'm gonna say once the story arc hit the climax and/or her physical presence is needed. Like if there's a horde of Joker or Scarecrow zombies, or if Nightwing are buried under the rubble and there's no one else.
Mainly in Nightwing, since there's only two of them in Bludhaven, so she's gonna be the only one there to help.
Almost never in Batman as long as Tynion is writing because he already got an army in Gotham. Ghost-Maker being the closest, then Bertinelli, Harley, Selina, The Batgirls and The Outsiders. Only if all of them are incapacitated or busy will she join, that is, if she's not in Bludhaven at that time.
So I'd say at the end of Tynion's run, while in Nightwing it's possible to do it once per arc.