since she has total blindness just in one eye, right optic nerve lesion makes sense. The poor reactivity to light supports this because eyes receive light through optic nerve (CN2)

young woman with abrupt onset painful eye movements + decreased acuity + poor reactivity = optic neuritis = MS

Also notice they said the right pupil is poorly active to direct light

So maybe there's a Marcus Gunn pupil, which is when there's decreased bilateral pupillary constriction when light is shone directly into the affected eye, relative to the unaffected eye

• Young woman + eye pain with ipsilateral vision problems = Optic neuritis
• Optic neuritis (as the name implies) is due to inflammation of the associated optic nerve, with further proof that optic nerve is involved being the relative afferent pupillary defect (problem with light getting back to retina in this case)