They didn't actually bag her, that issue. After she bogged Batman down with henchmen, she completed her master plan for the evening, which was to play matchmaker for two of the detectives that had been chasing her for months. She let them catch her, with Ivy in the Batgirl costume arriving to collect her, before the Bat crew made it to that room. She knew it was only a matter of time, though, so she and Ivy skipped town.