- Daughter of Doña Mayor and her second husband, Juan Fernández de Andeiro, later known as João Fernandes, 2nd Count of Ourém.
- Juan I of Castile married her off to Fernando Álvarez de Osorio, son of Álvaro Pérez de Osorio. [Fernando, ch.134]
Chronicle entries in which Isabel [de Andeiro] appears:
Crónica de D. Fernando, ch. 134