It is actually common for vets to wait until females are a certain age to spay. This is because they need to ensure the rabbit is sexually fully developed internally to completely remove the ovaries and uterus.
At this point, separation is needed since, and I think deciding in that arrangement may bring a lot less stress, be more manageable, and much more safe for everyone involved. In terms of space, you can have them take turns in the free roam space, which can help off set them being in a more restricted space. If there is biting or harmful interactions through barriers/bars, you can try binder clipping or attaching a bedsheets or something like that to visually deter it, or create a double barrier so direct contact is not possible.
I know it is not ideal, but this is something that is pretty common. Prior to being sexually mature, many rabbits will get along with others without a problem. It is most likely her becoming hormonal that is starting this.
I will also mention that after she is spayed and recovered, doing the formal bonding itself can take a bit of time and requires separation as well. There is information on the basics of bonding in the RABBIT INFO section of the website. If this seems not doable for you months from now due to resources or space, some people opt to pay for a bonder to bond their rabbits for them.
In short, separation is probably what’s going to make them both happier right now. It is stressful for the rabbits themselves to work out dominance, especially when one is fixed and the other is not.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.