Here's a link to my female @ 6 months with measurements. Your dog is not thin in my opinion. The full German Import breeding, has a smaller frame. My girl is a monster compared to most male import dogs. Can't tell you why but I cut her back to only dry food and free feed now.
Bogard's Sehr Gut Isabella - Bella Arrived Today Announcement
Don't worry be happy, the animal looks sensational !!!!!!!!!