The Collaborative International Dictionary of English v.0.48:

Seamstress \Seam"stress\ (?; 277), n. [From older seamster,
   properly fem., AS. se['a]mestre. See Seam.]
   A woman whose occupation is sewing; a needlewoman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

seamstress
    n 1: someone who makes or mends dresses [syn: dressmaker,
         modiste, needlewoman, seamstress, sempstress]