Flipped Out On My Supervisor - Scared About Career Implications

Hi all - I'm an associate counselor & have been working at my current group practice for 6 mo. My supervisor (who is also the practice owner) is a narcissistic unethical bully - I could go into details but it's not really the point of my post & I don't want to get myself worked up over it.

I know we've all had experiences with profoundly shitty supervisors, but when I was putting in my notice last week she informed me I would owe the practice $6k for breaking the employee agreement (which states employees must remain with the practice for a year, otherwise they would owe $6k in "training fees") I was shocked because two previous employees who left(one of whom left two weeks ago) were not required to pay out.

Long story short I let my emotions get the best of me and I went off on her. I wasn't yelling but I did raise my voice.. I told her I was furious, that I had felt bullied by her, and that she hadn't done her job as a supervisor - I was so angry I was shaking. I'm going to consult with a lawyer about the employee agreement. I'm scared of paying the 6k (which I absolutely do not have) but more than that I'm terrified that she's going to find a way to seriously harm my career. I'm glad I stood up for myself but I'm upset that I gave a vindictive person in a position of power something to hold over my head. I'm also just generally feeling shame for not regulating my emotions as that's been a long-term challenge for me as someone with complex trauma hx.

My big question to you all is: have you ever lost it on a supervisor before? If so how did you handle the aftermath? I have a new job lined up already and they know and believe me that she's been horrible to me so I don't think she could hurt me there, but I believe she would have no problem going out of her way to throw me under the bus in some kind of fucked up way. I'm just scared - being a counselor is the thing I value most in my life and I am terrified and feeling out of control right now. I'm mad at myself that I let things even get to this point. Any advice/support/wisdom would be extremely appreciated.