Trying to figure out the name of a book or book series! Fantasy category?

I m trying to remember the name of a book or series of books that I started reading. The book I read was not the first in the series, I think it was the second or third. Main character is a young woman. Plot: Her father (the king) dies sometime during the book, and she becomes queen. Kings/Queens are bound to their kingdoms in this world, and the dukes/earls/barons are also bound to their dukedoms/earldoms etc, though to a lesser extent. There are also the Kings Guard (or something like that) which are chosen magically/intuitively. When the King dies and princess becomes Queen, she asks all of the old King s Guard to become Queen s Guard. Some stay, some don t, and she also chooses new ones. I think the next book focuses on a female --King s Guard who, despite doing her best to protect her King, failed to keep him from being killed and yet survived the attack (she thinks that she should have died protecting him, especially since he died), and so ends up leaving the palace/city in guilt/shame.

And I think the Author s last name starts with A to G, and most likely C,D,or E.