From Halopedia, the Halo wiki

Alizée is an associate or friend of Dr. Catherine Halsey, mentioned by Halsey in a family tree-style picture listing her most significant relationships in her journal. Precisely who Alizée is, or whether he/she is even human, remains unknown. It is possible that Alizée is an AI, as he/she is listed at the same level as Kalmiya, another AI.[1]