To determine if \( \overline{NO} \) is a constructed copy of \( \overline{PQ} \), Thuy needs to ensure that the lengths of the two segments are the same. Therefore, she must measure the length of one segment and check if the other segment has that same length.
The correct response is:
She must measure the distance from point \( O \) to point \( Q \) using a compass and place the compass on point \( P \) to see if point \( N \) is the same distance.
This response correctly describes the process of using a compass to compare the lengths of the segments.