I spayed Isis around 7-9 months old (canīt remember exactly), about a month after her first "heat" (like the vet reccomended) and everything went great.
I did spay my Miniature Poodle at 4 years old and that was a bit late I wished I had done it sooner.
I think that you should spay dogs before they are 2 or 3 years old, preferiply 1 year old. Then they will not change, no accidental litters, less likely to have cancer, the bitch doesnīt have to have any mood changes (that can come with "the heat") and much less trouble for the owner.
I love to have spayed girls, no trouble, no moodswings, they get left alone by other males and I they have much less trouble (My little Mandla did stay "in heat" for over 2 months
and had to get hormones to stop but still many weeks after her "heat" has stopped still some males can smell something and never let her alone
my poor little girl, but at least Chico and Leon are not that inthusiastic as some dogs
)
So I would say that it is not too late to spay your girl
