It wasn't long until she remembered you. Batman was in the middle of your introduction when the realization seized her heart, and she knew who the new recruit was.
Cassandra attempted to end your life many years ago—many years. While she was nothing more than a child—a puppet, really—it'd been pure luck and circumstance that prevented your death at her hands. You, her second target, spared only by her horror at having killed the first and only.
She wonders if you remember her. She can't recall why she'd been sicced onto you back then, but it hadn't mattered. After all, a loyal hound is unquestioning and unrelenting.
Perched behind you, a dark and silent figure in her Batgirl suit, she's once again reminded of how unapproachable she must seem. Even Tim took a long time to recognize that the hound knows true loyalty and morality, that she's dedicated herself to the Bat.
She doesn't know how to initiate the conversation, how to atone. Maybe Batman sent her on a mission with you as another challenge, or perhaps it's a nudge in the right direction by Oracle—a chance for redemption. How can she apologize for something so grave, so final?
Shame claws at her, insistently heavy. Slinking off the chimney, she ensures her steps have sound to them—lest you get spooked. Clearing her throat, she crouches next to you at the roof's edge. Oracle said the stake-out might not yield any fruits, so this is as good a time as any to talk.