About 1844 she married and removed to Brussels. Here she came into an entirely new atmosphere and her manner of painting was changed. She sought to free herself from all outer influence and to express her own feeling. She studied color especially, and became an imitator of Rubens. She gained in Brussels all the medals of the Belgian expositions, and there began two historical pictures, "Peter the Great and Catherine" and "Maria Theresa and Frederick the Great." These were not finished until after her removal to Paris in 1853. They were bought by Prince Demidoff for the Russian Government.
She obtained her first triumph in Paris, at the Salon of 1853, by a portrait of Rachel. She represented the famous actress dressed entirely in white, with the worn expression which her professional exertions and the fatal malady from which she was already suffering had given to her remarkable face. The critics had no words for this portrait which were not words of praise, and two years later, in 1855, Madame O'Connell reached the height of her talent. "A Faunesse," as it was called, in the exposition of that year, was a remarkable work, and thus described by Barty:
"A strong and beautiful young woman was seated near a spring, where beneath the shade of the chestnut trees the water lilies spread themselves out upon the stream which flowed forth. She was nude and her flesh palpitated beneath the caresses of the sun. With feminine caprice she wore a bracelet of pearls of the style of the gold workers of the Renaissance. Her black hair had lights of golden brown upon it, and she opened her great brown eyes with an expression of indifference. A half smile played upon her rosy lips and lessened the oval of the face like that of the 'Dancing Faun.' The whole effect of the lines of the figure was bold and gave an appearance of youth, the extremities were studiously finished, the skin was fine, and the whole tournure elegant. It was a Faunesse of Fontainebleau of the time of the Valois."
Mme. O'Connell then executed several fine portraits--two of Rachel, one of M. O'Connell, others of Charles Edward and Théophile Gautier, which were likened to works of Vandyck, and a portrait in crayon of herself which was a _chef-d'oeuvre_. She excelled in rendering passionate natures; she found in her palette the secret of that pallor which spreads itself over the faces of those devoted to study--the fatigues of days and nights without sleep; she knew how to kindle the feverish light in the eyes of poets and of the women of society. She worked with great freedom, used a thick pâte in which she brushed freely and left the ridges thus made in the colors; then, later, she put over a glaze, and all was done. Her etchings were also executed with great freedom, and many parts, especially the hair, were remarkably fine. She finished numerous etchings, among which a "St. Magdalen in the Desert" and a "Charity Surrounded by Children" are worthy of particular notice.