For a small pin corsage, Jennifer should pick a ribbon size that is proportional to the overall size of the corsage and doesn't overpower it. Generally, a ribbon width of around 1/4 inch (approximately 0.6 cm) is considered suitable for small pin corsages. This size allows the bow to add a decorative touch without overwhelming the corsage itself. However, the final decision depends on Jennifer's personal preference and the specific design of the corsage.