Puppy's loose there baby teeth just like human children loose their baby teeth.
They wont fall out all at once, it will happen over time and usually the adult tooth will push the baby tooth out.
If some baby teeth dont fall out naturally you will have to get them pulled, the best time to do this is while having her spayed.
If you are not planning on breeding her you really do need to get her spayed.
When I first got Poppy I didnt want to get her spayed because I was too frightened to put her under an operation incase anything happend to her.
Now after reading up on the subject I realise it is more dangerous to NOT get her spayed then it is to let her have the procedure.
When a female is in heat dogs from miles around can smell her and its pretty much impossible to keep them away from her unless like John Stelting said you keep her locked up (which Im sure you dont want to do
).
Hazel will have much more freedom if she is spayed because you wont have to watch her 24/7 and keep her close to you for fear of her getting pregnant.
If she DID get pregnant it could be very dangerous.. I knew a bit about breeding dogs before but nothing about breeding yorkies.
I have now learned that yorkies usually need help with the whelping and sometimes the worst happends and you could loose the pups, the mother or both.
Its just too risky, so unless you are planning on breeding her then I really would suggest you get her spayed.
I will be getting my Poppy spayed as soon as she's old enough.