Philippa joined Gaunt's household in time for his ~1372 marriage to Constance of Castille, whose father's violent life was later the subject of one of Chaucer's writings (O Worthie Pedro...).
Philippa & Geoffrey's son, Thomas Chaucer, was one of the supporters of the new reign of Henry IV, Gaunt's son, who took the throne by force from his cousin Richard II. Together with his cousins, the Beauforts (offspring of sister Katherine and Gaunt), they formed an important role in solidifying Henry's government.
Philippa's pension is collected for the last time in ~1386 and it is assumed that she died shortly thereafter.