The Chameleon by Diane Burton

Legally Blond meets Mata Hari.

Socialite Jileena Winslott appears to be the spoiled, bubble-headed daughter of an industrial magnate. In reality, she’s her father’s smart, savvy aide, who yearns to run the family business. When her father sends her on a covert mission to the Outer Rim, she has the chance to prove herself. But he insists she take along a fake fiancé—the man she’s secretly loved for years.