Star Crossed, by Elizabeth Bunce

Escaping from Green Men soldiers after a botched theft results in her partner's death, Digger convinces a boat of young nobles to help spirit her away, thinking they are helping "Celyn" escape from convent school.  Willing to leave the city of Gerse behind for awhile, Celyn becomes a maid to one of the nobles, a younger girl named Merista who is about to be presented to the marriage mart, and goes with Meri to reunite with her parents, exiled for the last several years for their part in a plot to overthrow the king and the corrupt church. 


As the family waits out winter in their remote fortress, Digger continues her sneaking habits, liberating small trinkets to fund her escape and discovering secrets hidden by the family and their guests.  Blackmailed into giving up some secrets by an alleged family friend who is seeking to destroy Merista's father, Digger finds herself trying to protect herself and her own secrets while also protecting the family that has so willingly taken her in, keeping secrets about the forbidden magic Meri displays, the new rebellion being plotted against the despotic king, and the wounded prince hidden in secret chambers around whom all the rebels' plans revolve.

Slow to start, but filled with twists, turns, treachery, surprises and action, this is a very satisfying fantasy with a well-rounded heroine and elements of espionage, mystery, and suspense.

Sequel is Liar's Moon.