Considering how highly esteemed Otherworlders were in this world, it could be seen as downright rude that they had yet to give her a title. Others may have complained, but Elara could immediately guess why the King and Queen had been reluctant to give her any kind of power.
She was tied to Caspian.
As far as they knew, she was his lover and would marry him, and now she was his fiancee and their marriage was all but guaranteed in their eyes. Any power they gave to her could be used to aid Caspian whose power they were desperately trying to cut down.