It was 10.30 a.m. and Sophie was in a critical condition. The emperor would later report that he and Elisabeth found her “debilitated but completely calm”. The night before, the dismayed parents learned from Sophie's attendants that “the poor child had [suffered] a great deal”. Based on the available data, we know that when the parents arrived, she was completely dehydrated and her kidneys were already failing. There was nothing more to be done: at 3 p.m. Sophie went into agony. Her “involuntary cries”, as Franz Joseph would later tell his mother, were signs of impending death. Her parents kept vigil at her bedside. The doctors, aja and nanny also gathered in the dying child's room. Several times, Elisabeth tried to elicit a reaction from her. She talked to her, asked her questions. Shortly before her death, she asked her again: “Baby, where is Papa?”. But she could no longer speak. In response to the question, she merely “turned her beautiful, deep eyes towards him [Franz Joseph]”. In her last minutes of life, Franz Joseph pressed a crucifix into her small hands and Elisabeth placed the cross, which had always been under her pillow when her daughters were born, under Sophie's. Shortly afterwards, her daughter stopped breathing. The “Baby” was dead.

Winkelhofer, Martina (2022). Sissi. La vera storia. Il camino della giovane imperatrice (Translation done by DeepL. Please keep in mind that in a machine translation a lot of nuance may/will be lost)

ON THIS DAY, IN 1857, ARCHDUCHESS SOPHIE FRIEDERIKE OF AUSTRIA DIED AGED TWO-YEARS-OLD. She was the eldest child of Emperor Franz Josef I of Austria and his wife Duchess Elisabeth in Bavaria. Accompanying their parents, Sophie and her younger sister Gisela went to Hungary for a two-months tour. But soon after their arrival, Gisela felt ill with fever, and a day later also did Sophie. The beginning of the tour was postponed for ten days. Gisela recovered, but Sophie worsened, and her father called upon an experienced doctor from Vienna to attend her. She was diagnosed with typhoid. After some difficult days Sophie improved and seemed out of danger, so the Imperial couple left, but only days later while in Debrecen they received an urgent message informing them that their daughter was very ill. They rushed back to Buda, where they found their daughter already at death's door.

Sophie's body was embalmed, but on the orders of her father, her internal organs weren't removed as the traditional Habsburg mortuary rites required. Her coffin was exhibited in Buda, where people was able said goodbye to her for a whole day. After the viewing, her remains were taken to the Capuchin Crypt in Vienna, the traditional burial place of the Habsburgs.