"That woman isn't me."
"Who is she then?"
"Well, she's obviously an impostor."
"Who is she then?"
"Well, she's obviously an impostor."
An impostor or pretender was a person who pretended to be someone else in order to deceive another.
In 2266, a transporter accident aboard the USS Enterprise created an evil duplicate of Captain James T. Kirk. The duplicate acted as an impostor of the other Kirk. (TOS: "The Enemy Within")
Dala and her partners, Mobar and Zar were con artists who acted as impostors of Captain Kathryn Janeway, Tuvok and Chakotay of the USS Voyager respectively in 2376. They pretended to represent Starfleet, even going so far as selling memberships. (VOY: "Live Fast and Prosper")