Short answers, pulled from the story.
The Greek name Nephthys derives from the Egyptian phrase nbt-ht, which translates to Lady of the House or Lady of the Temple. This title likely describes her function rather than serving as a personal given name.
Nephthys appeared depicted as a kite or as a woman with outstretched falcon wings during funerary rites. She served as a morbid-but-crucial force of heavenly transition allowing the pharaoh to become strong for his journey to the afterlife while her magical spells were necessary for navigating the Duat region of the afterlife.
Recent Egyptological research questions whether Nephthys was truly married to Set despite common assumptions. Plutarch's De Iside et Osiride mentions their marriage but early Egyptian sources offer very little specific linking evidence.
Ramesside pharaohs built or refurbished a temple called House of Nephthys of Ramesses-Meriamun in Sepermeru during the 19th Dynasty. Another House of Nephthys seems to have existed northward in town of Su closer to Fayyum region, and a temple also existed in Punodjem where prophet Pra'emhab lamented his workload administering both House of Set and House of Nephthys.
Temple texts from Edfu, Dendera, Philae, Kom Ombo, El Qa'la, Esna corroborate her identification as supreme goddess of Upper Egyptian Nome VII. She held name Nephthys-Kheresket while presiding over Mansion of Sistrum in Hwt-Sek known as Diospolis Parva.