A pimp attacked an 18-year-old woman with a knife at a hotel last week because she “wasn’t working,” police said. Braintree police said Joao F. Vincente, 24, of Roxbury, attacked the woman Wednesday at a hotel on Rockdale Street. The woman told officers that she worked as a prostitute for Vincente and that he threatened to kill her during the attack, police said. Vincente was arrested and charged with several violations, including assault with a dangerous weapon and deriving support from prostitution, police said. Police also arrested a companion with Vincente, Mikeala M. Brunke, 19, of Dorchester, on a warrant for sexual conduct for a fee, the statement said.Travis Andersen can be reached at email@example.com. Follow him on Twitter @TAGlobe.