Snakes are horrible for eating rats,
but dogs are great, because they eat lambs.
Yes.. yes.. I see the difference! Dogs only eat animals that are maimed and destroyed to the point of being tiny dried bits sealed in plastic bags!!!
Next time tell her that you'll start grinding the rats up, drying the resulting meaty mash, and then you'll feed THAT to the snakes. When she goes "Ewww!!!" tell her that's what she feeds her dogs and cats.
I tell people that their dogs and cats eat other animals too, my snakes are just more honest.