Berthe was born into a family of comfortable means; her father was a prosperous attorney. Deeply devout, Berthe longed to become a Sister of Charity, but it was not to be. During her youth, her father suffered severe financial reversals and Berthe was obliged to work to help support her family. She offered her disappointment as a sacrifice for the sanctification of a priest of God's choice. This proved to be Father Louis Décorsant, a French priest who became one of her spiritual directors and close collaborators.
Berthe's life was marked by physical and spiritual suffering. At the age of 10, after her First Communion, she told her teacher, a nun: "I must suffer a great deal, I must be like Jesus." The nun asked: "who told you that?" The child replied: "the little Host which is my wonderful Jesus." In addition to painful illnesses and accidents, she experienced fears, doubts, perplexities, and diabolical persecution. At one point, during World War I, while praying, she was hurled down a stone staircase by an unseen force, yet her life, miraculously, was saved. She heard hissing in her ear: "I shall fight you to the end, obsessing minds, hardening hearts, feeding passions."
By all accounts, Berthe was a delightful character, combining spiritual fervor and common sense, humble, cheerful, thoughtful, attentive to others, loving and deeply sincere. She was a splendid cook, yet, from the age of 38, lived only on Holy Communion. At one point, when she was lodging in a convent, a nun who shared her room was instructed by her superiors to observe if Berthe took any food in secret. Despite her initial skepticism, she found, after a year's observation, that Berthe really ate nothing, only drinking, in the morning, a cup of coffee (soon rejected), and, in the afternoon, a small glass of wine.
Berthe's revelations often had a political character, dealing with the spiritual dimensions of national and international events. Msgr. Pieraerts, court chaplain during the reign of King Albert I, was one of her spiritual directors and close friends. Berthe reported that Christ requested Belgium's consecration to the Sorrowful and Immaculate Heart, as a remedy for the country's political and moral ills. Shortly after World War I, according to Berthe, Our Lord made this striking statement:
Internal strife is more rampant than ever in your country. It is being fanned by the evil seeds sown by the invader; it is fed by egoism, pride and jealousy, malevolent germs which can only generate moral ruin. I continue to have pity on a country that defended its honor at the cost of the greatest sacrifices, and on a sovereign faithful to his duty. To save this nation, I have wished, and continue to wish, that it should be solemnly consecrated to the Heart of My Mother....(The Sorrowful and Immaculate Heart of Mary: Messages of Our Lord to Berthe Petit, Franciscan Tertiary, 1870-1943, 2004, p. 51)