What Breed Is My Dog?

I got my puppy about a month ago. She was advertised as a Shepherd x Collie x Unknown Mix.

She's 3 months old and I definitely see signs of GSD in her, like peppering in the fur and her ears, but I'm unsure as to what kind of Collie. She's growing little bits of white on her chest, ears, and tail, She's fairly small, only 12 pounds. She's also incredibly quiet, she doesn't even bark while playing. Any help would be great! Thanks!