Isabel Luísa of Portugal was born on 6 January 1669 in Lisbon to Peter II of Portugal and his first wife Maria Francisca of Savoy at the Ribeira Palace. The palace was destroyed during the 1755 Lisbon earthquake. She would prove to be their only child, though I cannot find any information if Maria Francisca ever conceived again or if she perhaps suffered an injury during Isabel Luísa’s birth. As the heiress presumptive she received the title Princess of Beira.
Her unfortunate nickname ‘The-Always-Engaged’ came from the constant quests for her hand but never was one candidate successful. Candidates included Victor Amadeus II of Savoy, Gian Gastone de’Medici, Charles II of Spain and Louis, Grand Dauphin.
Her mother died in 1683, and her father remarried in 1687 to Maria Sophia of Neuburg. Her status as heiress presumptive was threatened by this new marriage as a younger brother could take her place. Peter and Maria Sophia had eight children including five sons.
Isabel Luísa would only live to see the first two children born, and her status as heiress presumptive disappear. She would tragically die of smallpox in 1690. She was first buried in the Convent of the Francesinhas before being moved to the Royal Pantheon of the Braganza Dynasty.