Wow, what a day you had! I'm glad you were able to get your bun to the specialist. It at least gives you an accurate idea of what's going on. I know it's easy to blame ourselves and second guess decisions that we've made, but it's hard sometimes to know what to do in the moment, and it's not always obvious how serious something might be. You care about your bun and tried to do the best thing for her. Even if you had brought her in earlier, it still could have turned out the same. A spinal injury is no easy thing to deal with or treat in a rabbit. It's not something that can just be mended like a broken bone, and even that is no easy thing when it comes to rabbits.
So why exactly did the vet get the impression that Coco might be in pain? I certainly don't get that impression from anything you've written about her. You seem to be very aware and in tune to this little bun, and I would think that if any one would know if something was wrong with Coco, it would be you.
It's not true that rabbits don't show pain, they can just hide it very well, especially to those that aren't very familiar with them or know what to look for, but there are always signs. Subtle clues that can tip you off if you are very observant and know what to look for. Little things like sitting a bit differently than normal, squinting eyes, not eating like they normally would, not moving around normally, just seeming like there is something a bit off. I don't know, but you seem to be really close to Coco and know her really well. I would think that if anything was off with her, you would know it. Remember also that your vet isn't seeing Coco behaving like she normally does at home. So you are going to be the one that knows best if something is wrong. You need to make sure to be the one that sticks up for your bun and explains that she is happy and doing well, to the vet. Know the behaviors that show she is happy, comfortable, and doing well, like happily eating her veggies, having snuggle time with you and the boys, grooming them and you, note all the behaviors that show these things and convey them to the vet. The vet can only go off of what she sees in the exam and what you tell her. And remember, the vet is an advisor, but you are the one that makes the ultimate decisions for Coco.
I think your vet is trying to be helpful, you just need to better convey the situation so your vet understands that Coco has a good life and is happy. And even if she is in some pain, that can usually be managed with pain meds if it isn't too bad. Honestly, if a rabbit is in severe pain, there's no mistaking it, if you understand rabbits at all. But these things can sometimes be hard for a vet to determine accurately, when a rabbit is stressed from being at the vets, and is not acting like it normally does at home. So when you see your vet again, make sure to share how Coco is at home, and all of the good things that show you she is doing well.
The acupuncture sounds like a good idea. I've read of some buns having really positive results. I don't know if Coco has any feeling in her back legs at all, but if she does, I've also read of hydrotherapy being helpful, if you happen to have someone in your area trained to do this with rabbits. Maybe your vet would have some info on it, as it should be done under a vets supervision anyways.
I'm sorry the appointment was so upsetting, but I think with better communication with your vet, you both may be able to find something that can help improve Coco's condition. Just based on what you've conveyed about Coco, I see no reason at all why pts should even be a consideration at this point.
im blogging from my phone and sometimes the auto correct doesn't work so some of my words might be all over the show so bare with me 
