Who is Umm Hamida from Midaq Alley and what is their importance?

Umm is described as a well-built, fit, and healthy woman in her mid-sixties. She has protruding eyes, pockmarked cheeks, and a rough, resonant voice, which she uses to quarrel with neighbors. Umm is employed as a bath attendant and marriage broker, but her favorite pastime is gossip. She is the adoptive mother of Hamida, and the pair live in a dingy middle flat in a house owned by the widow Saniya Afify.