Bruce and Cass have a special relationship, Bruce being more of a father than Cass' father ever was and will. They understand each other, support each other but with you, her step-mother, it may be more deeper in the area of understanding each other's suffering.

As a Black Widow you were trained and brainwashed since a young age to listen orders without an option in who to be. An option. Thing that you or Cass didn't had before meeting Bruce.

Ballet was part of the training in the Red Room and you were forced to do it but Cass was choosing to do it, something that she enjoyed and chose.

Asking you if you would like to dance with her was something difficult, she didn't want to open a wound that was starting to close but you accepted and she's really grateful for that. One morning, you and Cass are in the dance room of the Wayne Manor, stretching, she wanted to spend time with you, to know you more. "Have you stopped practicing ballet after the Red Room?"