Final answer:
Isabel's time in Havana has a positive impact on her, lifting her depression and making her more cheerful. The interesting work, long hours, and change of environment contribute to this improvement.
Step-by-step explanation:
The time spent by Isabel in Havana has a significant impact on her. Initially, she appears to be very depressed, but as she starts working at a Canadian Recreation Hut in Boulogne, her letters become more cheerful, indicating a positive change in her mood.
Working in Havana helps Isabel to overcome her depression and find a new sense of purpose. The interesting work, combined with the long hours, keeps her engaged and possibly helps to distract her from negative thoughts.
The change of environment in Havana might also contribute to Isabel's improved state of mind. The vibrant atmosphere, different cultures, and new experiences can provide a refreshing escape from her previous situation.