First are you sure that she is getting fat or is swollen from retaining water? If she is eating as much as you think, I would try Totally Ferret. It fills them up better and they eat less. I found this to help my one that was getting too heavy. They do have a senior which can be given to overweight ferrets too. You might try just feeding them separately, instead of having it out all the time, also. I am sure if they were raised together, it would be very stressful for them to be separated. Try to increase her activity. Play chaise and tug of war with her; anything to get her active. I hope this has been of some help. Phyllis and the four Wigglies, Faith, Hope, Charrity and Generosity [Posted in FML issue 2419]