Is it permissible for a woman observing 'Iddah to use a comb to comb her hair, and what is the evidence for that?

A woman observing the 'iddah (waiting period) after her husband's death is permitted to comb her hair without using perfume, henna, or any other adornment. This is based on the hadith where the Prophet, peace and blessings be upon him, said to Umm Salamah: "Do not comb your hair with perfume or henna, for it is a dye." She asked: "With what shall I comb my hair, O Messenger of Allah?" He replied: "With sidr (lote tree leaves), you should wash your head with it."

The intention is that merely combing one's hair is not considered adornment, and she is permitted to clean herself, remove unwanted hair, trim her nails, wash her head, and comb her hair.