Well, I do agree that your baby was obviously bred without the true Yorkie traits in mind so recessive traits cropped in, BUT I am totally shocked to find out she doesn't have any other breed in her.
I am sorry that I said she was mixed, but it is cool to know she isn't.
As for her hair, it could be some issue going on, but it could also just be "normal" for Minnie. Know what I mean? If she has some recessive genes that were eventually bred out to show up in Minnie..it could just mean that she's going to have different hair.
DNA test or no DNA test, Minnie is an absolute doll and I know she's gonna be spoiled for the rest of her days. I am so glad you have your answer now, though. Now, you can move forward