Is your wife hunting in a cold region(is she wearing a big bulky jacket)? What type of varmint are you(you & her) hunting: gophers, coyotes, wolves, fox?
Have you had a look at the .17 Remington round?(trappers #1 choice)
Since you were considering .243, were you thinking possible deer hunting?
What type of terrain are you planning to hunt: open plains, heavy brush, valleys,?
Does your wife have any experience shooting anything(rifle, shotgun, etc.) in her life?