The Senator has angered the Emperor, and so the Emperor has requested Sidonia's presence at the Chrysanthemum.
Sidonia's father, the Senator von Impyrean, has angered the Emperor
"You have destroyed this family with your actions! ...And our family? And our daughter? We will lose everything!" (pg 33-34)
Sidonia's Mom plans to send Nemesis in disguise as Sidonia to the Chrysanthemum to protect her daughter.
Nemesis is talking with Sidonia's mom
"I will kill you before I let her go to her death." (pg 37)
"I intend to send you to the Chrysanthemum in her place. You will be Sidonia Impyrean." (pg 37)
Nemesis Disguised as Sidonia, meeting the Emperor
Because Nemesis is sent in place of Sidonia, she meets the Emperor and the rest of the Senators and is exposed to the tensions rising in the Empire. This will set the stage for the rest of the conflict in the book.