If she's at home alone a lot and is unable to train with a gun, perhaps a doberman (or similar model) would be a better choice than a gun. And, maybe whatever gun she's most comfortable with (presuming there is one) as a backup.
A security system sign, a beware of dog sign, and a deep bark coming from the house should deter pretty much anyone.
Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety. ~B. Franklin