The fair island

As different as possible in character from her identical twin, Alaine
Marsland was persuaded to take Estelle's place on a cruise to the Greek
islands. Away from the drudgery of her work, relaxing in the sun,
enjoying the sightseeing, Alaine blossomed--and learned that life
could be beautiful. Cimon Duris, boarding the ship at Pireaus, added
the perfect romance...
Then, along with the realization of her love for Cimon came an equally
disturbing discovery. It was Estelle who had sown the seeds of the
trouble -- but it was Alaine who was about to reap the harvest of
revenge!