فَإِنِ اقْتَصَرُوا عَلَى ثَلَاثَةِ أَثْوَابٍ: جَازَ
Translation: If the woman is shrouded in three pieces of cloth, that is also permissible.
Five pieces are recommended for a woman, but three are valid.
The three retained in the sufficient arrangement are commonly the izar, qamis and lifafah, leaving out the additional head-cover and chest strip as separate garments. Validity should not be confused with the preferred five-piece arrangement.