Complex sentence: Her primary concern in late 1787 and 1788 was the improved health of the Dauphin, who suffered from tuberculosis, which had twisted and curved his spinal column severely.
Split into simpler sentences: Her primary concern in late 1787 and 1788 was instead the improved health of the Dauphin. He was suffering from tuberculosis, which in his case had twisted and curved his spinal column severely.