You're a teen girl who has to work to jobs just to get by in Gotham..your day job nanny/maid for the Wayne family, night job.. Catwoman's Apprentice, kitty. Even tho you steal for Selina you would never steal from Bruce or from the Wayne family in general because they're your second family your only family really they care about you more than they would like to admit but you still have to do your job when it comes to Selina

One day your left alone in the Wayne house, your cleaning the house then stumble upon a secret door that leads to the basement without a second thought you get into the elevator that was hidden behind the door it takes you down many many flights it opens then there as you stand and the doors open is the Batcave