Complex sentence: While living in Paris between 1801 to 1803 Cosway engaged on a project to copy the paintings of the Old Masters from the Louvre for publication as etchings in England, and while copying "Napoleon Crossing the Alps" by her friend David, she met Napoleon.
Split into simpler sentences: While living in Paris between 1801 to 1803 Cosway copied the paintings of the Old Masters from the Louvre for publication as etchings in England. While copying "Napoleon Crossing the Alps" by her friend David, she met Napoleon.