She was born in Schaerbeek (now a district of Brussels) under German occupation during the First World War. Her mother, a British nurse, was shot for helping soldiers escape from Belgium to the neutral Netherlands. Andrée de Jongh became, like her mother, first a nurse and during World War II a heroine rescuing Allied soldiers.

The resistance fighter recalled that after the Germans reoccupied the country, she could not sit back. She decided to help Allied soldiers, mainly airmen, return to Britain. The route from Belgium led through France, over the Pyrenees to Spain. The first successful smuggling Andrée de Jongh made in August 1941, at which time she transported a Scottish officer – James Cromar from Aberdeen and two Belgian officers from Brussels to Spanish Bilbao.

Andrée de Jongh organized a whole network of people helping the Allied soldiers. At first, the British government was distrustful of her, suspecting the young Belgian woman of being a German agent, but the rapid success of her network soon led to it being funded by British intelligence. This was necessary, as one smuggling operation cost the organization more than $2,000 (at the present value of that currency).

The Comet Line was the largest network of its kind organized in Western Europe. During its three years of operation, more than 770 people were smuggled, using various transportation routes. The most commonly used route, laid out by Andrée de Jongh, led from the Belgian capital Brussels or Lille in France to Paris, then through Tours, Bordeaux, Bayonne and the Pyrenees to San Sebastian. Further routes ran to Madrid and Gibraltar, and more than 400 people were smuggled through this route. Over time, however, the German intelligence service succeeded in arresting numerous members of the network with the help of a network of collaborators. On January 15, 1943, while carrying out a smuggling operation on the French-Spanish border, de Jongh also fell into the hands of the Germans. During the following investigation and torture, the Belgian woman revealed who she was and what she did for a living, but the Gestapo interrogator did not believe the story she told him. This saved her life, and the young woman was sent to the Ravensbrück concentration camp.

When the Gestapo, the German Secret State Police (German: Geheime Staatspolizei) realized who they had in their hands, they tried again to find her, but de Jongh was very sick and malnourished in the camp, and had also hidden her identity, so the Germans were unable to find her in the crowd of women imprisoned in the camp.

The Belgian woman survived the war, and was liberated from the Ravensbrück camp with the arrival of the Red Army on April 30, 1945. She died at the age of 91 years in Brussels in 2007.