Hey there! 
I really really suggest spaying her. I know its scary, but i think possibly putting them through cancer, a shorter life span, and stressful false pregnancies is even more scary and it really sucks for them. After they turn a year old, they have between 70-90% chance of getting Uterine and Ovarian cancer. In addition, false pregnancies are super stressful for them and can be super stressful for their owners as well because they get more territorial, snippy, and moody around those times.
There are measures to take before surgery, to increase the chances of her survival. Number 1, is finding an experienced vet who knows what they’re doing. Ask your vet how many spays and neuters they do weekly or monthly, how many has she lost, and why she lost them.
Sometimes things happen during surgery that are out of anyone’s control, some bunnies have something wrong genetically that could affect the outcome of their surgery. I just pulled up a great article from the House Rabbit Society, which ill link at the bottom, and it says this to the question “When is a rabbit too old to be spayed or neutered?” that i think made a great point about taking pre-cautions to spays and neutering in general, not only if the rabbit is older, but also if you are worried or previously lost a bun to the surgery, etc.
” Veterinarians will have their own opinions on this, but in general, after a rabbit is 6 years old, anesthetics and surgery become more risky, but that doesn’t mean it can’t be done. Simply consult your veterinarian regarding your rabbit’s health and circumstances, and opt for pre-surgical blood work.
It is always a good idea, in a rabbit over 2 years of age, to have a very thorough health check done, including full blood work. This may be more expensive than the surgery, but it will help detect any condition that could make the surgery more risky. This is especially important if anesthetics other than isofluorene are used. “
We finally got our adult female bunny, Pumpkin, spayed back in February. It was the best decision we could have made. She’s a little bit older than Peter, Pumpkin is about 5 or a little over. The surgeon said it was a big surprise she didn’t have any tumors or cysts, she was truly one of the lucky ones (and in turn, so were we, because the surgery went even more smoothly). There are countless bunnies whose lives have been saved by being spayed.
We were so worried about losing her because you always hear horror stories about animals who don’t come back from anesthesia.
But we haven’t regretted getting her spayed, her behavior has changed and so has her attitude. Before she would be on edge all the time and be really snippy, and now shes more laid back and wants pets. She’s more relaxed, and i believe she’s way more happy now.
I hope this helped!
Spay/neuter article from HRS: https://rabbit.org/faq-spaying-and-neutering/