In Chapter 3 of The Horse and his Boy, Aravis says that thanks to the forged letter she sent, her father wouldn't be looking for her until after she'd left Tashbaan. But when she is in Tashbaan, Lasaraleen says her father is there, already looking for her. So presumably he hasn't received the letter yet. (Maybe her slave girl woke up earlier than she thought.) 

Recently, this made me wonder what his reaction will be when he gets it. He'll know it's fake and that Aravis must be responsible. Would he punish his secretary for helping her? Actually, he'd probably do that eventually anyway. Even if Aravis plan had been entirely successful, the truth was going to come out sometime. In a culture where getting drugged earns you a beating, the punishment for forging a letter from a Tarkaan must be way worse. 

If so, it seems weird that Aslan would punish Aravis for leaving her stepmother's slave to be beaten but not for leaving the secretary, who, unlike the slave girl, was loyal and devoted to her, to his grim fate