Doppelganger

During a robbery, a bank guard is shot. The license of the getaway car is traced to Architect Iris Reid. When the police arrest Iris and show her security footage of the robbery, she sees her own face looking back.

Scrambling to defend herself against an airtight case, Iris discovers that her mail's been diverted to an abandoned apartment in the next town. She's able to find a clue there that allows her to pick up her doppelganger's trail.
This third installment in the Iris Reid mystery series introduces Rosica, Iris's beautiful but treacherous doppelganger, a sinister creature guaranteed to send a shiver down the reader's spine.
But someone is watching her every move.

"The plot becomes more unnerving as it progresses, and an impressive twist leads to a lengthy final act featuring Rosica at her most ferocious...Cory's concise prose establishes a consistent pace that never wavers, and even her descriptions of architecture are exhilarating." The KIRKUS REVIEW