Deringers were designed in the early 19th century for crooked gamblers to shoot folks that caught them cheating at poker, from a distance of a few feet across the card table.
It's not an accurate target shooting pistol, and you'll get tired of it quickly. My advice is to get your wife a Ruger SP101 in .38/.357, and for quite awhile let her shoot inexpensive .38 wadcutters. The SP101 has slightly smaller grips and dimensions as compared to the GP100, and should be perfect for her. It's still accurate and manages recoil well, however.