Mexía was an active member of many scientific societies, including the California Botanical Society which she joined in 1915, the Sierra Club, the Audubon Association of the Pacific, the Sociedad Geográfica de Lima, and the California Academy of Sciences. She was also an honorary member of the Departamento Forestal, de Caza y Pesca de Mexico. She also guest appeared as a lecturer at various scientific organizations in the San Francisco Bay Area on account of her riveting accounts of her journeys and her skillful photography lending visuals to her content. Her specimens can be viewed at the California Academy of Sciences (main collection), the Academy of Natural Sciences, Philadelphia, the Field Museum of Natural History, the Gray Herbarium, the New York Botanical Garden, the Smithsonian Institution, the University of California, Berkeley, and the U.S. National Arboretum, as well as several museums and botanical gardens throughout Europe. Her personal papers are preserved at the California Academy of Sciences and at the Bancroft Library at the University of California, Berkeley.