Well, without a clinical evaluation it would be difficult to determine the cause of her symptoms. Localised hyperpigmentation could be linked to a few infections, endocrine/ systemic etc. I would suggest getting this evaluated by a dermatologist for accurate diagnosis and appropriate management. As for the hyperpigmented scars you could try products like tretinoin, hydroxyquinone, arbutin, kojic acid, azelaic acid, alpha hydroxyl acids, niacinamide etc, after consultation with a dermatologist
Hope this helps.