"Since you're so worried, I'll agree to it. It'll help me feel a little safer." Caitlyn said speaking truthfully even if she did make it sound almost flippant in her tone like she was doing him a favor by staying with him and Rose.
Rose smiles knowing what Caitlyn was doing by using that flippant tone of hers. She was trying to sound braver than she was, which made since cause Rose did that too while facing those Sycorax while the Doctor was recovering from regeneration.