"It's a long way back," she said softly, indicating the challenge or difficulty of returning to their previous state or position. Her tone suggests a sense of reflection or perhaps concern about the journey ahead.
Nick responded with a shrug and an act of reassurance by holding her hand more firmly, implying confidence that they have already made significant progress. His words, "Not so far as we've come already," reinforce that despite the difficulty, they have overcome much and can continue forward.