@Prince of Seraphs Is there any reason to send a message for her with it? And I think it'd be up to Belle if she's around or not.
It's a simple delivery, an exchange of goods. One of those everyday Court kinds of things that a ruler doesn't need to attend to personally. I suppose if Belle wanted to Arys could accompany the convoy but really the only thing that would accomplish would be to put her in harms way for no apparent purpose. She has servants for a reason. Think of it this way. If the convoy was important enough for Arys to personally accompany it to ensure it reaches its destination why then would Nyx not be joining the Spring side of it as well?
It is possible for Nyx to send a message for Arys with the convoy but the most logical thing to do in that case as well would be for Sini to relay the message to the goblins who would then give it to Arys.