To determine if segment \( \overline{NO} \) is a constructed copy of segment \( \overline{PQ} \), Thuy should ensure that the lengths of the two segments are equal. The most appropriate response would be:
She must measure the distance from point \( M \) to point \( Q \) using a compass and place the compass on point \( M \) to see if point \( O \) is the same distance.
This is because she needs to check if the length from point \( M \) to point \( Q \) matches the length from point \( M \) to point \( O \). If they are equal, then \( \overline{NO} \) can be considered a constructed copy of \( \overline{PQ} \).