Welcome to YT
! Shire sounds darling - I love her name...is that influenced by old England, btw?
As for spaying - even though she is 6mths, you may have some time to wait bc she is tiny. Tinies often develop later, so there may be time before her first heat. Also, what is happening w/ her teeth right now, bc you'd want the vet to remove any baby teeth during her spay too - so usually, you watch the teeth a bit for timing the spay too.
My Pfeiffer is 6mths old and we were just at the vet last week, and my vet said we should wait another month or 2 bc of teeth - she thinks we have more time yet for development.