I just got a new mini aussie and I'm not sure if she's fat or if mini aussie puppies her age are supposed to be a little chunky. She's 13 weeks and weighs 13.2 pounds. She's not obese or anything, but she does have little fat rolls back by her hind legs and I've always heard that's a sign of a dog being overweight. Mom is 11 inches & dad is 14 inches, both are very trim. Anybody know what a healthy weight for her age would be? Am I worrying too much?