Book about a girl who is the secret twin sister of a princess

Question

I’m looking for a book. The book is about a girl who is a twin to the princess. She is the main character in this book. No one knows she exists and her only job in life is to protect her sister because her sister is going to be queen. Only a few workers around her castle know she exists.

Then they start to get threatened and to make a peace deal with another kingdom. The king says he will send over the princess, his daughter, as a way of showing that he will not harm their country and trusts them. Instead, they send over the twin, who had a cool name that I think started with an 'R.' The twin has to pretend to be her sister, even though she was trained in combat and not anything fancy, or manners like a princess should have.

She gets there and ends up falling in love with the prince from the other country thing and they run away together, because her dad, the king, is planning on bombing the other country.

That’s all I can remember. Also, there may be like multiple books to this series, but this is the first book I am looking for, so please help.

Answer 1

Scott Westerfield's Impostors

Deception. Risk. Betrayal. Redemption. Master storyteller Scott Westerfeld is at the top of his game, and back to his most famous realm. A New York Times bestseller.
Frey and Rafi are inseparable . . . two edges of the same knife. But only one of them is ever seen in public.

Frey is Rafi's twin sister-and her body double. Their powerful father has many enemies, and the world has grown dangerous as the old order falls apart. So while Rafi was raised to be the perfect daughter, Frey has been taught to kill. Her only purpose is to protect her sister, to sacrifice herself for Rafi if she must.

When her father sends Frey in Rafi's place as collateral in a precarious deal, she becomes the perfect impostor. But Col, the son of a rival leader, is getting close enough to spot the killer inside her . . . .

It is apparently a spinoff of his Uglies series, set in its future.

Found with a search for novel princess's secret twin is her bodyguard