There are cases with rabbits who have no uterus or under-developed uterus. Was there any mention of seeing ovaries? It is the ovaries that actually produce the hormones, I believe. It is possible that they haven’t developed yet, yes. I haven’t been with a female rabbit through a spay so unfortunately I cannot give an idea of the age expectancy, but I have generally read that there are indeed times when spays occur too early, resulting in unsuccessful/incomplete spays.

I will note that your neutered male rabbit who “just wants to fight with her” may continue doing so, even after she is fixed. While having both rabbits fixed is a foundational step, it is usually not the eliminator of aggression towards each other — that comes from steadily progressing through the bonding process.

How odd…. waiting longer and rechecking does seem like the right move. In my mind it would be important to know for sure to make sure she didn’t end up getting a reproductive cancer later in life.

As for the aggression, has that been in neutral territory? It’s common for rabbits to be aggressive towards each other in non-neutral space.

There are some cases where the female can’t be spayed for medical reasons and has still been successfully bonded, especially before spaying was a common procedure.

I think I would wait until her spay is sorted out. I am also thinking that if for whatever reason her uterus never forms but she still has ovaries, her hormones will be more stable once she is more mature.