On 12 September 1428 at Alcolea de Cinca she married Infante Peter, Duke of Coimbra (9 December 1392 – 20 May 1449 at the Battle of Alfarrobeira), a younger son of John I of Portugal.

During her husband's regency for his nephew, Afonso V of Portugal, the marriage of the couple's daughter Isabella to the King was arranged.

The threats of the powerful Duke of Burgundy were conjoined to the pleas of Peter's daughter, the young queen Isabella of Coimbra, who pleaded her husband to have mercy on her family.

Against the advice of the powerful Braganzas, Afonso V relented (partially) in 1450 and allowed the widowed duchess Isabella of Urgell to reside in Montemor-o-Velho and Tentúgal (Philippa was allowed to reside in a cloister in Odivelas, although apparently she later moved in with her mother).

Peter of Coimbra's remains were allowed to be re-buried at the Aviz dynasty necropolis at Batalha Monastery and the dowager-duchess Isabella of Urgell was granted a royal pension for the remainder of her years.