The inspector general’s office is focusing on Rollins’ attendance at the Democratic National Committee event in July as well as her use of her personal cellphone to conduct official business, according to two people briefed on the investigation, which has been underway for weeks.They were not authorized to publicly discuss the ongoing investigation and spoke on condition of anonymity.As district attorney for Suffolk County, which includes Boston, Rollins pushed ambitious criminal justice changes, most notably a policy not to prosecute certain low-level crimes such as shoplifting.The Senate Judiciary Committee deadlocked on her nomination last year before she was confirmed by a 51-50 party-line vote, with Vice President Kamala Harris breaking the tie.Investigators also have asked about Rollins’ trip to California in June to speak at CAA Amplify, the annual gathering of entertainment, business and political figures run by one of Hollywood’s leading talent agencies, the Creative Artists Agency."