If you trust your breeder and they are definitely Allie's parents, it just could be she's a bigger Yorkies than normal. Just like there are tiny Yorkies from regular sized Yorkie parents, there are bigger Yorkies as well. Just more to love!
Also, some Yorkies grow faster than average too, but the growth may slow down faster too. So it all just depends. I'm sure you'll love her the same no matter what!