They MAY have a scar if it was done recently. The vet may be able to shave and tell.
I don’t believe there is anything full proof as far as behavior.
The only absolute real way to tell is maybe by x-ray (but you would have to verify that with the vet) or to have her put under anesthesia and an incision done if you don’t have the paperwork from the vet of course.
Here has been my experience with this:
1. I had a little netherland, Chloe, who was definitely spayed by one of my vets and she ended up having some issues – she had what was obviously an ectopic pregnancy and when he did an x-ray to see what was going on, he could see where he put the “clips” in the tubes. And he also was able to see the unborn fetuses, but that is another story….so that’s the only reason I’m guessing about the x-rays, but I’m not expert about that.
2. I had a very large NZW, Maxine that I got from a shelter so I took her in to be spayed and the vet opened her up and she was already spayed which was bizarre for a big old red eyed white rabbit.