She doesn't appear thin to me, but as you mentioned you can see the rib outline. I am wondering if deworming her every 8 weeks may be a bit too frequent. It may possibly have something to do with it.
I don't know what type of pellets you feed other than 10%, my thought is adding a little corn oil to her diet, soaking the pellets and mixing the oil in, may help put on a little additional weight. Another thought is to add a small amount of alfalfa if you think it's appropriate. Or good old fashioned oats. :)
An imbalance in calcium/phosphorus intake ratio could have something to do with her not assimilating the nutrients she's getting as well as she could. I assume she has a salt/trace mineral block.
She's a beautiful girl, by the way :)
Last edited by DRichmond; 05-08-2012 at 02:43 AM.