Stephling totally has a trust fund set up by Bruce. And when/if she's kidnapped and people are sent to her rescue, they find out that she has a "secret uncle" who's been teaching her martial arts.
Especially as every other Bat will be going Bzuh? about why Tim's so into this case (Except maybe Babs).
Bruce would know. He's made it his business to keep an eye on the kid and feel guilty since Steph's death.