For its part, Portugal, a new-born country, managed to secure an important alliance with Flanders, and European recognition.

Theresa brought a considerable dowry, something that helped Philip manage his war with France for a couple of more years, before making peace in 1186.

Theresa lived in one of the most luxurious courts of Europe, in which Philip patronized Chrétien de Troyes, author of a famous cycle of Arthurian stories and one of the fathers of the Holy Grail theme in literature.

However, like Elisabeth of Vermandois, Theresa never gave birth, and after Philip's death, the county passed to his sister, Margaret I, and her husband, Baldwin VIII.

After Philip's death in August 1191, Theresa, holding extensive dower lands in southern and coastal Flanders, was powerful enough to challenge the rule of her sister-in-law and brother-in-law, provoking unrest among the public in her dower lands by raising the taxes and becoming a central figure of the part of the nobility opposing the succession of Margaret and Baldwin, but was forced to relent.