I’m very sorry about Missy 🙁
I think trying a slightly larger space (as long as it’s neutral), and allowing a little nipping is a good idea. Nipping is fine, as long as it’s not escalating to a fight. Having a bit more room will give you some time to react, and will give them a bit more room to move around each other.
The other thing you can do (which tends to help the human as much as the buns), is when they ask each other for grooms, pet them both a lot and swap their scents. This makes them think the other rabbit is grooming each other and helps keep everyone calm and happy. Sometimes real grooms will even follow. Eventually you have to ease off the petting, but in the early stages it can really help!
So when they approach each other, be ready to pet pet pet. When they move away from each other, let that happen. Mounting and nipping is also OK to allow, but stop hard biting, circling, and prolonged chasing.
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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.