There's enough caution in her question--caution that is not aimed directly at him--that Caspian blinks at her in surprise, not a little pleased that she seems concerned for his welfare.

Still, she looks worroed, and while he thinks she needn't be, he nods and tries to explain.

"'Tis a chance, of course, and it's possible we never will reach the edge, or even come close to it, or find even one of the seven lords. We might have to turn back, if our food or water won't last us as long as we hope, or if foul weather comes up. Never fear, lady, we will return home again. I would not abandon Narnia, even for the Utter East."