Carter has two beds because she and Brooke were friends once, and Brooke slept over a lot.
This friendship ended when Donny two-timed Carter and Chelsea. Brooke squealed to Chelsea, who undid Carter's friendship with Brooke and her reputation. Carter is defensive towards Rosie because she doesn't want any more unwanted attention. After ending her friendship with Chelsea, Brooke will try to patch up things with Carter.
Based on the above guess. Carter's hatred of Princesses came from her father's job.
With all the times he left town to protect some Princess, Carter started blaming them for not having enough quality time with him.