It’s a combination of all factors, including the vet’s comfort level. Some vets may feel comfortable spaying a female before she’s 2.5lbs, but if this is something your vet specifies, it’s probably within their experience, as well as their comfort level. Neuters are much less invasive, but obviously Wick’s max weight is 2lbs, so Wick’s vet had to be comfortable, and they were, with neutering an 800g rabbit.

I think when she hits puberty and behaviors start forming, that’s a good time to say, let’s do it now, unless she doesn’t weigh enough or she is combating another health problem.

She’s still young (if I remember correctly), so postponing a spay by a few months won’t put her in risk for cancer development or anything like that.

Do it at 6 months, as she’ll be developed at that time and the surgery won’t be as much of a risk. I think doing it before then will cause her unnecessary stress, especially if they open her up and find out she’s not developed yet. Then she’ll have to go through the process all over again.

I’ve had more than 10 rabbits spayed and neutered. My rule of thumb is 6 months for the females and 4 months for the males. If she is smaller than a normal size for her breed, wait an extra two months.