Masquerade by Christopher Hoare

Masquerade is the second novel in the Iskander series of alternate world/SF adventures that feature the strong female storm-crow Gisel Matah, a security agent for the castaway Iskanders on the alternate Earth called Gaia.

She is now seventeen and a trainee officer aboard the Sirius, Iskander's oceanographic launch...now a covert operations craft. She still hasn't completed training when an urgent call sends her and Sirius several hundred miles up the River Megalon to investigate the abduction of the Grand Duke of Bergundene. An old flame appears, the Empire's top spymaster seeks to trap her, covert operations abound, and the action becomes intense. No explicit sex, suitable for teenage and adult readers.

The Iskander series were originally published in Canada by Double Dragon and the rights for all five novels have reverted to the author.