It’s not recommended to bond bunnies if one of them hasn’t been spayed or neutered but there are success stories out there. I think it largely comes down to personality (of course) and how hormonal the intact rabbit is.

I am a bit confused about your Mum’s reasoning behind not wanting to bond before. If bunnies are truely bonded, you should be able to leave them unsupervised and not have any concerns. Was she concerned about a bond breaking?

If you get a 2nd bun, you’ll need to go through the proper bonding protocol so you would need to let the new bun settle in and then pre bond for at least a month. Possibly longer as you’ll be dealing with an unspayed bun so you might need to go slower. Honestly I think it would be better to bring Willow inside. If she’s lonely, she needs more socialising and as bonding is such a lengthy process, her lonliness won’t be ‘fixed’ quickly. Is there any way you could have her inside?

I really think you need to try to get your bunny inside. You could keep her in a pen or build her a cube condo and only let her out with the cats when you are supervising. A lot of bunnies and cats co-habit peacefully including mine.

I will say from experience that it’s REALLY hard to bond unfixed rabbits, but possible. How long ago did her bondmate pass? If she’s still in mourning, she might be more accepting of a new bun friend.

It’s great that you’re trying to do what’s best for your bun!

I’m just going to give some plain advice, not trying to be rude at all. You have a rabbit that doesn’t get enough attention/interaction and is stuck outside partly exposed to the elements. Putting a second rabbit in the same situation because your first one is lonely and cold, isn’t a solution. All that means is that now you have two rabbits in unfavorable conditions, instead of just one. What I think you need to do instead is using your money and resources to improve the life of the rabbit you already have. As others have said, that includes housing her inside permanently, where she can be safe and you can give her the attention she needs. You being homeschooled is perfect, that means you can spend lots of time with her.  If the cats are a problem, just make the room Willow will stay in a cat free zone.

As far as the spaying issue goes, of course it’s possible that Clover had an underlaying issue which caused her to pass during surgery, but without a necropsy there’s no way to tell. I think it’s much more likely that the vet who did the surgery wasn’t as rabbit savvy as they claimed. Of course they’re going to suggest an underlaying issue as the cause, rather than admitting that they don’t have much rabbit experience and killed her with the anesthetic. The chances of that are much higher than both of your buns having a hereditary problem that would make surgery unsafe. I would suggest that you find a new, rabbit savvy vet. Tell them about what happened with Clover, and have them do all the tests they deem necessary to rule out any health issues. Then, given the approval of the vet, I would go ahead with the spay. Unspayed females have an above 85% chance of developing reproductive cancer by the age of 3-4. Compared to that, the odds of a rabbit having major hereditary issues are much smaller.

A spay is invasive surgery and thus there’s risk involved. Just do plenty of research and go from there. I’m very sorry you lost Clover, and I understand that it makes it that much scarier to possibly have Willow spayed. Just don’t let that keep you from considering all the options.