Final answer:
The nurse should advise the client not to make a decision about their wedding until they feel better and can cope with their diagnosis.
Step-by-step explanation:
The best response by the nurse in this situation would be D. "These are your feelings now, but don't decide until you feel better and can cope." This response acknowledges the client's concerns and emotions but encourages them to postpone making a major decision until they are in a better emotional state. It also offers support and reassurance that they don't need to rush into deciding about the wedding.