“Amanda Clarke” is alias of the real Emily Thorne, and is also known as “Fauxmanda.” After meeting David Clarke’s daughter in juvenile detention, the pair teamed up and switched identities — all part of the larger revengenda at hand.
Fauxmanda came into the picture after Frank Stevens, the Grayson’s private detective, discovered her true identity. She hit him over the head with a shovel, killing him to keep Emily’s secret. The juvy-grad-turned stripper then ran to the Hamptons to tell Emily Thorne (aka the real Amanda Clarke) all about it.
After arriving in the Hamptons, she caused nothing but trouble for Emily, nearly revealing their secret, pretending she was actually Amanda Clarke, and dating Emily’s childhood love, Jack Porter. Although she leaves twice — once when Emily sends her off, and another time when she is fleeing a murder scene with Takeda — she always comes back. In the Season 1 finale, we find that she is pregnant with Jack’s child, and will surely cause plenty of trouble in Season 2.