My daughter 16 is a hogkins lymphoma survivor of 2 yrs. Had a CT and it says relative stranding on right side of neck. What does this mean?

Unclear. If your daughter has had treatment, she has most likely had other ct scans since completing therapy. The scan should be compared to prior scans to look for new findings. Discuss this finding with her oncologist to find out for sure what he/she believes this means.
Please compare to. Older ct scans. It very well may be changes related to her treatment. Please make sure the current ct has been compared to any older scans, and discuss your concerns with her oncologist. Ask them what they think it means.