Well, it's not specified exactly what caused Jenny's death in Love Story. It might have been a combination of factors related to her poor health condition.
In ancient times, consumption was a serious disease that was usually considered incurable. Due to the limited medical technology in ancient times, people's understanding of consumption was not scientific, so it could not be effectively treated. Phthisis, also known as the modern day's lung cancer, was an infectious disease that was highly contagious. The patient would often cough up blood and his lungs would be severely damaged. In ancient times, serious cases of lung cancer would cause a high fever. If they were not treated in time, the patient would die very quickly. However, the development of modern medicine had brought about the emergence of anti-inflammatory drugs, which made it possible to effectively control and treat the disease. Therefore, modern people did not necessarily die from consumption. However, in ancient times, the treatment of consumption was very difficult, so it was considered a fatal disease.