She’s not in West Seattle, but I used Jenny Manes in Magnolia for my wedding dress in April. She did an excellent job on a delicate fabric (Chantilly lace with silk underneath), so I know she has talent!
Her website mentions that she does curtains, so she might be able to help. If anything, she might be able to give more info about other seamstresses in the area.
http://www.jennymanes.com/