A .38 is a very good choice. But, there is no need for light loads because she won’t know whether the hole is big or small until after the shooting is done. No matter what the load, the holes in range targets will look the same.
A hollow point + round ought to work, and it doesn’t look any scarier than other .38 rounds. In fact, you can tell her that hollow point “thingy” is a kinder, gentler round because of the hollow tip that ball rounds lack ;-) The bottom line is that you want your wife to be safe.
Dallas Area Robber Transit, would not want any of my family riding that death train.