Per this email interview with MTV.com, she isn't.

From: Damon Lindelof

...allow me to answer your question. Is she a robot?

She is not.

_{^{'PROMETHEUS' SECRETS SPILLED BY CO-WRITER DAMON LINDELOF}}

Per this email interview with MTV.com, she isn't a robot, but the resemblance to David is also not a coincidence.

From: Damon Lindelof

Vickers. Yes, she does look like David. Yes, this was intentional.

What better way to piss off your daughter than to build the male equivalent of her? But enough about daddy issues (seriously, Lindelof, we get it!), allow me to answer your question. Is she a robot?

She is not.

_{^{'PROMETHEUS' SECRETS SPILLED BY CO-WRITER DAMON LINDELOF}}