I'd look up the statistics of double barreled derringers ability to stop a determined threat.
I would not carry this as a primary defensive handgun. Much better primary options out there that can be comfortably concealed and accurately shot by a wife or anyone for that matter.
Designs of this kind have been around ever since personal (non-matchlock) firearms have existed. They are usually called "belly guns" because, as a last ditch defensive weapon, they are often used in a contact range setting, muzzle pressed right up against the assailant.
Even though it may seem like "just a .380", at contact range, a whole new world of ballistics is opened up. Remember, when a gun is fired, not just the bullet comes out of the barrel...Hot propellant gases are ejected in front of and behind the projectile. In a contact shot, almost the entire discharge of flaming gas is also injected into the target along with the bullet, creating massive wound cavities. Contact range GSW's are extremely nasty because of this. John Ross explains this in tremendous detail in Unintended Consequences when the Jewish partisans were fighting for their lives in the Warsaw Ghetto. The description of the effect of that .38 revolver fired straight into the Nazi guard's stomach is very memorable.