I do not know about Australian Cattle Dogs as I have always had smaller girls and I usually had them spayed three months after their first season - except for my current little one who was spayed at six-months of age before she had a season, but due to many loose dogs around it was decided to spay her early, as soon as she reached 6kg in weight. Hopefully someone more knowledgeable than I will be able to advise whether than would be the appropriate age for your girl or not.
There is no necessity or advantage in a bitch having a litter before being spayed. There should not be any personality change, nor should a bitch gain weight after being spayed. All operations have a risk of complications, so does giving birth. Sex to an animal is just a biological urge. Happiness has nothing to do with it [unlike in humans! ]
Bs. tell that to any woman who wanted to have a baby who couldn’t. my dog put on one collar size within weeks of being fixed . So again wrong, personality changes immediately and has since, not even subtle . again try telling a woman who gets a hysterectomy who has hormone issues related to it that it doesn’t affect moods. The complications were they tore her uterus and she bled and almost died , so yeah ! Big deal when she wasn’t almost dead before she went in , guess you just threw that in for good measure did you ? biological urge ? Oh dear we humans are complicating things with our big brains (not wagging tails)
Anyway ...... Did you ever read the book called ‘a dogs tale’? I suppose I really liked it because it was written from the perspective of a dog and it’s journey. That’s where I’m coming from with all this, we’re all mum and dad fur parents .
There are lots of articles on the pros and cons’ of neutering/spaying do lots of research before reaching a decision. https://www.linkedin.com/pulse/long-term-health-risks-benefits-associated-spay-neuter-michele-o-hara
My vet spayed Kyrie just before she turned six months old, and thought that sooner was better. There’s been no personality change in her that I could tell, other than her maturing a bit as she passed the puppy stage. That said, she was three in late May, and still is quite playful. Same with the wife’s mini-Aussie.