Especially since she was driving
When you listen to Kim's speech during the 9-1-1 call she made alleging the racial slurs from the "frat house" when they drove/walked/sat by the house, she didn't sound drunk at all. When the cops came, if she kept her distance from them of a few feet, no way would they think she'd been drinking, especially if she freshened her breath with something while waiting for the cops to get there. They were there to deal with Mangum and their understanding was that kim was just a good samaritan who gave a drunk woman on foot a ride to a safe place. All the cop wanted to do was clear the call.