Lean is a good thing but I think she is too skinny as her rib cage really stands out. Let us know what you feed her. You seem to give her plenty of food but either she is not able to digest this fully if this is a good quality food. Or you are feeding her a lesser quality food. So please let us know the brand(s) you feed her.
Deja, GSD, sable WL, female, born 11 / 2013
Cam, Rough Collie, sable, male, born 8/2015