Cass was mildly relieved and more than a bit honored that Bruce thought of her as his Batgirl. It was quite an accomplishment, both to hear that she'd achieved what she'd set out to do, and to actually hear him say that out loud.
But she didn't quite see how it didn't matter that he'd known about Barbara, or that Barbara had been Batgirl for a while. Barbara had even admitted that it had been a case of thoughtlessness on her part.
"One Batman," she said. "One Nightwing. One Robin. Never two. At a time. I thought ... one Batgirl. No one said." She took a breath. "No one ask ... how I feel. Say nothing. Then ask ... why I run."