I do not know the relation of Egyfacia to Margarita.
The spelling of her name (Egyfacia) varies in all records.(there's Eyiaca, and Kiricaca?)
After her husbands death, she moved first to Martinez. and when she got older, she moved in with her sister, the famous Juanna Briones de Miranda in Fremont (Santa Clara Co Census-1880 listed her as Kiricaca Briones). She died in Martinez in 1885 age 81.
She did have a son Angel Briones (b 1829) he was married to Frances Martinez, who was a daughter of Vicente Martinez and Nieves Soto.
Hope this helps,