A medium mouse is not the width of her stomach. I know it might LOOK like that but it isn't an adult mouse is not the width of her stomach either. If you are feeding FT take the mouse by the tail and by the head and stretch it gently. You will see that they are a lot smaller than they look frozen. If you are feeding live the same thing goes.. Once the snake has killed the animal the body is obviously limp and much smaller than it looks alive or frozen. Mice are very lean too. Another reason why are you aren't seeing the animal poop as much because it is using everything in the meal it has every two weeks. Switch her to weaned rats for a month and then go to smalls. She will put on size pretty quickly. I will reiterate the fact that you will run into biting and constant searching around the enclosure if you don't up her prey size.