That's one of the nice parts of Yorkie ownership...you get to choose.
Her hair may be thin and look mussed up now, but even grown out, it's gonna look mussed up a good bit of the time. She's a Yorkie...a terrier.
Mine look groomed for about 30 seconds after I finish with them after a bath...until I put them down...then, they go 'plowing' and when they get done, you can't tell their coats have ever seen a comb or brush.
It is difficult to wait out the hair growing stages, and this is where the choice comes in. Prissy is young enough that you can opt for a puppy cut now and grow it in later if you want to. It is hard to imagine what they will look like and so makes choosing what to do agonizing, but it is amazing how good they look in different cuts. I lucked out and found an excellent groomer who talked about it with me and we selected a 'path' to a look we think I will like when the coat is all grown in. But, if you cannot decide, flip a quarter...then put some pix up so we can see what you decided.