After one of their worse arguments, Princess Rarity starts to avoid Twilight, spending more and more time in her room. That wouldn't be quite as much of a problem, if not for Twilight's duty to protect the Princess at all times.
Written as my second entry in Monochromatic's Raritwi contest and set in her Bodyguard AU, which in turn is based on Earthsong9405's AU that I've never actually read.
Cover art once again generously provided by Multiversecruise.