UNC: Asari Diplomacy

UNC: Asari Diplomacy is obtained when you locate you enter the Athens system in the Artemis Tau cluster. You need to find Nassana Dantius on the Citadel. Once you've spoken to her, head to Sharjila in the Macedon system, in the Artemis Tau cluster.

Once you eliminate the hostile forces, proceed to the upper level. You will find evidence that the asari helping the slavers, and Nassana Dantius are in fact sisters. You need to return to the Embassy Lounge on the Citadel to confront Nassana with this evidence.