**Core Concept**
Post-traumatic stress disorder (PTSD) is a complex psychological condition that can develop after an individual experiences a traumatic event, such as an earthquake. This condition is characterized by symptoms like flashbacks, nightmares, and avoidance behaviors, which can significantly impair the individual's quality of life.

**Why the Correct Answer is Right**
The woman's symptoms, including nightmares about the earthquake episode and feelings of terror at night, are indicative of PTSD. These symptoms are thought to be a result of the individual's brain processing the traumatic event, leading to the formation of a memory that is difficult to erase. The hypothalamic-pituitary-adrenal (HPA) axis is activated, releasing stress hormones like cortisol and adrenaline, which contribute to the development of PTSD symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** Acute stress disorder is a condition that develops within days of a traumatic event, whereas PTSD typically develops weeks or months after the event. This individual's symptoms have persisted for three years, making acute stress disorder less likely.
**Option B:** Major depressive disorder can present with symptoms like anxiety and sleep disturbances, but it does not typically involve flashbacks or nightmares about a specific traumatic event.
**Option C:** Anxiety disorder is a broad term that encompasses various conditions, including PTSD. However, the specific symptoms described in the scenario are more characteristic of PTSD than a general anxiety disorder.

**Clinical Pearl / High-Yield Fact**
PTSD can be diagnosed using the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria, which include symptoms like flashbacks, nightmares, and avoidance behaviors. It is essential to recognize the complex interplay between psychological, social, and biological factors in the development of PTSD.

**Correct Answer:** B.