Wandering Star by Russell Romina

Orphaned, disgraced, and stripped of her title, Rho is ready to live life quietly, as an aid worker in the Cancrian refugee camp on House Capricorn.
 
But news has spread that the Marad--a group of unbalanced Risers determined to overturn harmony in the Galaxy--could strike any House at any moment.
 
Then, unwelcome nightmare that he is, Ochus appears to Rho, bearing a cryptic message that leaves her with no choice but to fight.    
 
Now Rho must embark on a high-stakes journey through an all-new set of Houses, where she discovers that there's much more to her Galaxy--and to herself--than she could have ever imagined.
 
And just when Rho has started to come to terms with the pain of losing Mathias, the stars deliver their most shocking surprise yet.