SOLVED. YA Fiction - Fantasy - Girl disguised as boy is the bodyguard of a prince. Spoilers below.

[Claire]

The only one who knows her identity is her twin brother, who dies.
The reason she is hiding her gender is because all girls over a certain age are forced into this breeding house.
She guards outside the prince's room. One night he has a nightmare, so she rushes in, thinking someone is attacking him.
Assassins break into the prince's room, so now she has to sleep in his room across the doorway.
Thanks for any help!

[Claire]

Heh, I actually figured this one out on my own. If you're curious, the book was Defy by Sara B. Larson.

[Anya]

thank you for sharing the title ; )

[Rainbowheart]

Defy for the link.