But the thing is, it doesn't work her past her current issues. Not at all. It helps her make up with Batman, sure. It doesn't do a thing to make her better prepared for the next boy in her life, and her relationship with Babs only gets worse throughout Horrocks' run (not that Horrocks ever seemed to have much respect for Babs or her importance to Cass to begin with). It's not healthy to pretend that she's totally okay now, or that what he and Cass did here was effective, when that's manifestly not true. What makes a coping strategy unhealthy is not typically the coping strategy itself. There's nothing physically detrimental to the human body in, say, always running away from your problems. The thing that makes a coping strategy unhealthy is that it doesn't work - it doesn't address the actual problem. In beating up Bruce until she feels better, Cass has completely failed to address the actual problems in her life. In pretending that was effective therapy, Bruce has encouraged her to continue to fail to address the actual problems in her life. In letting Bruce get away with that, the rest of the cast has encouraged her to continue to fail to address the actual problems in her life.
They let her use nails when screws were called for, and now she's got a shelf that won't hold together right and she's that much less willing to use screws next time.