I worked for the 'Snake Charmer' and had Cottonmouth,copperhead,Sidewinder as my friends. But they killed my unborn daughter and sent me into a coma. So i set out to mercilessly 'kill' them all.

This describes Beatrix Kiddo (The Bride) from 'Kill Bill' who worked for Bill (the Snake Charmer), and her codename was Black Mamba. The Deadly Viper Assassination Squad members had snake codenames: Cottonmouth, Copperhead, Sidewinder, and Black Mamba. Bill's Deadly Viper Assassination Squad killed her unborn daughter and put her in a coma, leading to her revenge quest. The question asks for her codename, which is Black Mamba.