In 1627, the Antwerp cloth merchant Peeter Stevens had his portrait painted by Anthony van Dyck. When Stevens got married a year later, he commissioned Van Dyck to paint this portrait of Anna as well. Anna was placed on the left, so that she did not have her back turned to Peeter. But actually convention dictated that the man should hang on the left and the woman on the right.
After Rubens, Van Dyck was the most important portraitist of his day. He was popular because he made his patrons look just a bit more beautiful and elegant than they really were.