We need more info to answer that question.
Where does she live? How close are neighbors and livestock? How about buildings?
If she lives way out in the country like I do you could use about anything you like. I can fire my 375H&H in almost any direction from my home with total safety.
If she cannot do that then you need to think about what is the range that can be known to be safe
In some areas the best coyote gun is a 20 gauge with #5 shot
In other areas the best may be a 6.5X284 or a 270 Winchester.