Begin with something familiar
Lay a shawl you like on a flat surface without stretching it. Record its width and the length of the woven body. If it has fringe, measure that separately. A single total length can conceal how much fabric actually wraps around your shoulders. Label the units beside each number rather than relying on memory.
Describe the movement you want
Measurements are more helpful when paired with a use. Do you want the ends to hang evenly while seated, enough width to cover both shoulders, or less fabric beneath a coat? Photograph or sketch the way you wear your existing shawl for your own reference. You do not need to put body measurements or a photograph into a public comment to explain the problem.
A request is the beginning
RARA’s Handwoven Linen Shawl entry gives you an original source to inspect for dimensions and care instructions. Its interest form can record an email and optional preferences; that does not mean this merchant offers alterations or has accepted a custom order. A useful note is: ‘I prefer a shorter woven body, excluding fringe; please confirm whether another length is available.’ Ask the seller to confirm feasibility and final dimensions before agreeing to a purchase. A clearly bounded request is easier to answer than ‘make it fit me.’