Please please PLEASE do not breed from your tiny girl - it COULD kill her
If you want another small Yorkie then go to a breeder who has smaller stock.....there are loads of really helpful folk here on Yorkie Talk who will guide you in the right direction
Personally I would take what your vet says with a pinch of salt.....they are experts in medical issues but when it comes to breeding know-how you need to speak to folk who have had yorkies for many years
And how much is ultrasounds and an induced labour going to cost?
Quite apart from the ethical and moral issues of inducing labour which, surely, goes against nature?
You could probably get a very nice healthy puppy from a breeder for what vet fees may cost AND at no risk to your beautiful wee girl