Some melanated people get darker very quickly with sun exposure. After I spend a day or two outside, I won’t get any darker after that. She’s probably the same. Also, skin cancer incidence is much lower in south India compared to the north, let alone compared to western countries (despite south India having higher UV exposure). Her ancestors lived in a sunny part of the world for tens of thousands of years, they evolved resistance to the sun, she will probably never get skin cancer.