Final answer:
Encouraging open communication about end-of-life wishes is important for someone with cystic fibrosis, due to the life-threatening complications associated with the disease and the lack of a cure. Transparent dialogues respect the patient's preferences, providing control and support during a challenging time.
Step-by-step explanation:
Based on the research in the text, the most appropriate advice to give your friend, who has a 20-year-old daughter with cystic fibrosis, is to encourage open communication and discussions about end-of-life wishes. This is crucial as cystic fibrosis is a genetic noninfectious disease with no known cure. Although medical interventions can help manage symptoms and extend life, ultimately the disease may lead to life-threatening lung complications, underscoring the need for open conversations about healthcare preferences, end-of-life care, and other sensitive issues.
Such transparent dialogues can help ensure that the young woman's values and preferences are respected, and they can also provide a sense of control over her treatment and final arrangements. Finally, it is important to acknowledge her awareness of her condition and to support her in facing her prognosis with dignity and support from loved ones.