When the watchtower's existence was brought up, a lot of things suddenly made sense. Why the building they were in wasn't heavily guarded, and where all that money in Bruce's secret Swiss bank account went. She just assumed he was making a Bat-Rocket or something, well she wasn't too far off. Unlike the others Batgirl wasn't upset, she was used to having secrets kept from her; just another quirk of being part of the Bat-family. Instead she just gave Batman a knowing look as she waited for the others to finish whatever they were doing.