She's so cute! She does look like a mix to me. I can't shake the impression, from the pics, that she is also much older than the breeder told you. Have you been to the vet with her yet? They can check her teeth and determine approximately how old she is by that. She just doesn't look like a 16 week old puppy to me, I don't know why, just a feeling
Regardless, I'm sure that she will bring you many years of love and joy
