Sharon Carter was a S.H.I.E.L.D agent. When S.H.I.E.L.D. fell, she then joined the CIA. Her main undercover identity was as a nurse which she was in when she first met Steve Rogers. She is also the neice of Agent Carter who worked closely with Steve during World War II.
She uses the same face as Leia's 2015 Endor variant redesign.