Hello, It would be good if your sister got treated by medicines but since you want her to be treated naturally, she can take food that promote healing like leafy greens, yellow fruits, oranges, meat, chicken, legumes, beans, whole cereals. Less of spice and oil. She can take vitamin B6, B12 rich food or supplements. She can take cool bath or shower to ease itching and pain of skin. She can apply natural numbing agents like aloe vera, clove oil, ice pack or cold compress. Baking soda & corn starch pastes help healing effectively. She is suggested not to share her toiletries or clothes with anyone. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician