Instead of taking your news report at face value I went around and have found several differing reports of the shooting.
According to WSB-TV, the local ABC affiliate in Atlanta, not only was there a marked Atlanta PD car in front of the residence but the narcotics officers who worked the warrant case were wearing police vests of the same type as those commonly worn by swat teams. I'm going to assume that this woman was not an idiot and bothered to look out one of the windows in her house facing the street. Seeing the Police car, when someone at the door claims to be police, you have even more of a responsibility to make sure who you're shooting at. I agree that had they just blindly broken the door down without announcing themselves the woman should have shot back no questions. But they did announce themselves and had a marked police presence. This stuff about how the police were wearing street clothes is just a smokescreen.