In this story, she was a mysterious burglar and jewel thief, who is revealed at the end of the story to be a young, attractive woman. She does not wear her familiar cat suit but this story establishes her as a femme fatale who both antagonizes and attracts Batman. At the end of the story, Batman is implied to have deliberately let her get away by blocking Robin from catching her.
Incidentally, there’s also this weird sequence in the story when Batman decides to moralize about guns by releasing four tied up goons to have a hand-to-hand fight with Robin.
Check out the story here: