I actually think that if Deb found out he was the butcher, it would make her completely question herself and everything she's ever known about Dex. I think she may even quit the force, because you can see how much she wants to be successful, but will be torturing herself over the fact that she has know the butcher all her life, but never been able to spot anything about him and realise who he actually is...
I won't kill my sister...I won't kill my sister...I won't kill my sister...