I'm not sure what size mouse they were feeding her. I believe she is undersized because yes they were feeding but only enough to sustain her, not let her flourish if you will. The first 3 1/2 feeding I bought normal mice...maybe about two inches long for the feeding. The couple small rats I have now are nice fat ones about 4 or 5 inches long. The mice didn't even make her look like she ate...the smaller rats give her just the slightest bit of a bump. With a better feeding routine I expect her to get a bit of a late growth spurt. Like I said...she eats like a champ.