"Tsarina" by J. Nelle Patrick

From Amazon.com:

"Natalya knows a secret. 

A magical Faberge egg glows within the walls of Russia's Winter Palace.
It holds a power rooted in the land and stolen from the mystics.
A power that promises a life of love for her and Alexei Romanov.
Power, that, in the right hands, can save her way of life.

But it's in the wrong hands."