This is genetics for her... she's been here since the beginning of the month and overfed on Science Diet and hasn't gained really anything. She would need a lot of food to put on weight. (Vet ruled out health problems) On APBTs she is at a conditioned shape (like what would be desirable for ADBA shows)
You very rarely see a APBT truly in shape unless you're into ADBA showing so often times when people see a ADBA conditioned dog they jump to skinny. Which is understandable, we were raised accepting greyhounds to be very lean but we're used to seeing thick bullies.
Here is a very fit, very healthy Staffordshire Bull Terrier
And this would be underweight.
You want to see muscle over the ribs, if they breath in then it's okay to see rib but at resting you shouldn't be able to count them. I'll use this dog since him muscles are very defined, at first he looks ribby but if you look closer it's muscle coverage.
[img]http://i28.photobucket.com/albums/c217/ ... lepic3.jpg
Let me know if I explained that badly.