I assume that a “hard pain” in the neck is severe neck pain. You have to be more specific in regards to the location of the pain and the timing. Is the neck pain centrally located (in the center of the neck) or does it radiate into the shoulder and down the arm? If both, what are the percentages of pain in the neck vs. the shoulder/arm? Is it 60/40 neck shoulder vs. 80/20 shoulder/neck or?
If the C6 and C7 nerve roots are compressed- your sister might have pain that radiates into the left shoulder and down the arm to the thumb side of the hand. If she bend her head backwards (extension)- this might cause increased pain in the arm and if she bends her head forward, she might gain some relief.
I do not understand what that 1.7 cm node is in the thoracic and lumbar spines unless it is a Schmorl’s node (an endplate fracture that is generally benign).