I’m sorry you are having such a tough time with them! You mentioned Bella is spayed, but can you confirm that Winnie is neutered? If not then that is your primary problem. My advice below assumes that he is neutered. Bella sounds like a fairly territorial rabbit in gerneal (those nethies are so fiesty!). Also the fact that she is blind in one of her eyes might make her a bit more fearful, and hence aggressive. Health issues in general can make it difficult to bond. Also keep in mind that rabbits are aggressive out of fear, so helping her realize that Winnie is not a threat is going to be the most important step.
You mentioned that stressing helped at first, so I would start by going back to this. Nothing too intense though! My first bond sounds very similar to yours and I did eventually get them bonded, but it took a long time. What worked for me finally was to start with SUPER short sessions, so that they wouldn’t have time to fight. I would first take them on some short car rides together in a bin, maybe 5 -10 minutes max. If they don’t fight in the car on the first day, repeat this daily for a few days (as long as the buns aren’t getting overly stressed out) with no other bonding sessions. If that all goes well, then add in a 2-3 minute session after the car ride. The goal is to end the session before there is any aggression at all. If the buns like to be petted you can also pet them during this time. If that goes well, repeat the same thing the next day. If that goes well, you can try skipping the car ride the next day, but again keep the session short. Then you will want to gradually increase the amount of time they are together. I recommend being pretty hands-on at first, so any time they approach each other, be ready to start petting them both. This will help build a positive association and make them feel like the other rabbit is grooming them. I would not put food in the pen at this point, just in case it causes aggression.
The space you use is extra important. It should be VERY neutral, meaning that it doesn’t even smell like your home. In really tough bonds I have even gone to a friend’s house to bond because my apartment was too small to have any true neutral territory.
.
.
.
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.