Originally Posted by BatLobsterRises
I think it's because Selina is portrayed as very street smart and "in the know" when it comes to that sort of stuff. I mean considering she is currently the best working theif in Gotham, she might have even had a "professional respect" for Joker being able to hit a mob bank and get away clean.
Yeah. If she wanted to know, or if it concerned her, she'd dig out the details. Selina had been in and out of institutions, and knowing the system in and out, and who could be under her roof, would be beneficial given her lifestyle. She became aware of clean slate, which was a mysterious item.