The option indicating that Pelvic Inflammatory Disease (PID) is least likely in the scenario presented is supported by specific clinical features of the case. PID typically occurs as a result of sexually transmitted infections and may present with symptoms such as abnormal vaginal discharge, fever, and more widespread abdominal pain. In this situation, the patient has a sudden onset of localized pain in the lower right quadrant, which is more indicative of other localized abdominal conditions.
Additionally, the patient's normal menstruation three weeks ago suggests that there may not be an ongoing infection or inflammation associated with the reproductive organs, which could lead to PID. Conditions like ectopic pregnancy, appendicitis, and peptic ulcer disease have symptoms that correlate more closely with the specifics of the sudden, localized pain described.
Ectopic pregnancy could present with acute abdominal pain, but the timing and the fact that menstruation was normal may decrease its likelihood. Appendicitis is a classic cause of right lower quadrant pain and presents acutely, making it a strong possibility. Peptic Ulcer Disease could also present with abdominal pain but is not classically associated with acute, localized sudden pain in the right lower quadrant in women. Therefore, PID is the least fitting condition given the circumstances and presentation.