Final answer:
Sarah is currently in the denial stage of Kübler-Ross's stages of dying.
Step-by-step explanation:
Kübler-Ross's stages of dying are denial, anger, bargaining, depression, and acceptance. Based on Sarah's statement, she is currently in the denial stage. This is evident from her disbelief in the doctor's diagnosis and her feeling of being fine without any noticeable symptoms. It is important to note that the stages of grief can occur in different orders and not everyone experiences all of the stages.