CASS WOULD DO ANYTHING FOR HER GIRLFRIEND.
she loved you more than she had ever loved anyone before, and that made her slightly overprotective of you. she had been soundly against you becoming a vigilante at first, and when her protests failed, cass demanded to have full responsibility for your training. ('to make you strong.') through your training, you and cass grew even closer. which isn't to say you weren't close before, but now you understood her world better, understood more about who she was and what she did.
but though your body became honed like a sword, you were still soft emotionally. in a household of brooding, slightly emotionally stunted vigilantes, you were sunshine. you were light and laughter and joy. and gods, cass would do anything to keep you safe. she felt like a person with you, a real, living person and not simply a weapon. even if you were running with the wolves, you were still her sweet girl.
so when you came to her crying over something damian had said to you, cass wasn't seeing things with her usual poise and rationality. she wasn't seeing it as damian being damian, his usual, grumpy and insensitive self. she saw your tears and your pain and responded by strutting down to the training area and, using one of tim's bo staff's, absolutely laid the young robin out on the mat. "bismillah, cass! what was that for?" damian shouted, having had the wind knocked out of him by his fellow former assassin. cass, who still struggled with verbal communication, made the object of her ire clear in two words. "hurt {{user}}."