This post answers the first version of the question, where the part "without fighting" was not included yet...
To start with: please don't let them meet repeatedly only to disturb them every time. Each time you disturb them it increases the bad memories they have with each other. These memories will make it much more difficult for them to find a peaceful way of living together.
Second, it is natural for rabbits to fight for their rank. And your situation of the dominant rabbit being ill and loose it's rank is a typical natural process. In nature the method of ranking is a method to proliferate the healthy and strong rabbits. Because this rabbits get more food, they will have more successful litters and offspring. Additional there are seasons, when fighting occurs, ie after cold periods, when mating season start, or when one of them starts puberty.
And third, I understand you fully. It is hard to watch them fighting, loosing fur and chasing around. I feel with you and wish that you will stand it. Because if you will not, they may never live again together and you need to give one away, or separate them completely. But in each case you would need to get new companions for them...
Now the good news: You have two females, both are fixed. In general this type of rabbit have better chance to overcome their fights and find a peaceful way. Also you wrote you have an enclosure, not a cage. This too gives you more possibilities to shape it in a good way, and them to have save places, they can hide from each other, if the aggression (periodically) comes back.
I will make my points in chronic order:
- shape the enclosure they both shall life in
- build a temporal enclosure, on neutral territory
- let them try to find a rank (+signs of hopeless cases)
shape the enclosure
If you have two rabbits which are not as peaceful as you wish, you need to have a special view to the enclosure. You do not want to have dead-ends, where one can trap the other. Do not only think about corners, think about houses with only one door, too. Also add "walls" they can hide behind, so they do not need to see each other the whole day. This will reduce the stress of feeling monitored by the other rabbit the whole time. Stress is one reason for aggression. To have a second floor in the enclosure (with more than one stair up and down -- dead-end) is a good way to give this safety (I will link some ideas and examples in the end). The enclosure should have minimum 6 square meters base area, or more if the rabbits cannot roam in a bigger area (garden, apartment) for a minimum 6 hours per day. In Germany the 6 square meters are law since last year and to have minimum 2 rabbits too. To reduce the stress, you should consider to make two feeding places. This can avoid aggression about food, both of them can have "their own".
build a meeting enclosure
If rabbits meet strangers (and you now need to consider yours strangers) the first thing they check is: is one of them hurting the territory of the other one? If this is the case, the "home" rabbit will start to fight without alternative and wants to defend the borders. This is not your aim. You want them to meet at absolutely neutral ground. As unknown for them as possible. You want them to feel a little bit puzzled, to feel a little bit alone. So they are happy to find another rabbit in this strange environment. If you have indoor rabbits, this effect can be reached by neutral ground at the outside. Also the bathroom, a garage, or the rooms of a friend are options you should consider. Important is, that none of the rabbits ever was there before, so none of them could think as "my territory" of this place. Also the size is important. Rule of thumb are 3 square meters per rabbit. But for you I would recommend it some way bigger. Smaller space make the process faster but could make it more rude. And more space slows things down, but also the probability to let them stay more calm is higher. The furniture of this temporal enclosure is also important. It should also not contain dead-ends, but hiding places to take a rest. BUT none of these things should be from the old enclosure (-- "my territory"). You can use cardboard boxes (two doors, as tunnel...) or other boxes (wood, plastics - to have the second floor, not as house). The ground of the whole enclosure needs to be not slippery (they will run a lot with changing directions). Flexible borders, as pen-fences can help you to react by making the enclosure bigger or smaller during the process (see next point).
find a rank
There will be chasing, there will be turning, scratching and biting. Fur may fly, some drops of blood may occur. This are no reasons to stop it (I am sorry...). If they do not start to interact, you may make the enclosure smaller and/or remove some furniture. If you feel, they have no break to breath, you may make the enclosure bigger and/or add furniture to hide/avoid eye-contact to get a break.
Reasons to stop the process would be:
- One of them gives up but the other one does not stop fighting. The "give up" one would place its head in a corner, or at the border, turning the back to the enclosure and does not leave this position anymore, but the second one would not stop biting.
- There would occur injuries, you need a vet for. They would not stop bleeding, are more than scratches, need to be sewn together by a vet. (Any injuries for which you as a human would take a simple band aid don't need help of a vet.)
- The rabbits fight weeks long without having peaceful times in between.
- One of the rabbits is petrified by the other. It does nothing else than running away, although the other rabbit is not chasing it. Even days after starting the process, there is no visible improvement.
If you need to stop the process, you need to find a new home for them. This means, you may have two separate enclosures for them with no contact (no view, no smell) and a new friend for each of them. Simple solution would be to give one away and get a new friend for the remaining one.
You described that your rabbits were grooming each other. This is a very good sign! They do this only when bonded, even if they fight again afterwards. I assume, that your submissive rabbit got to much "freedom" while the dominant one was ill. It is natural for the submissive one to try to rise it's rank if the dominant one gets weak. And if the dominant one can not rebuke, the submissive may become more and more impertinent. Now the dominant is strong again and starting to teach the submissive, but she doesn't want to give up the benefits. So each time the submissive does something inappropriate, the dominant one will give it a lesson. This can last a while, until both found and accepted a new balance of powers. I wish you patience! (Rabbits do not sleep the whole night, same as they aren't awake the whole day. So fights at night are possible too and do not have other significance than fights at daytime.)
Please let me know, if you have more questions about details!
general reasons for fights in bonded rabbits
- Mating season (even if they are both female they feel some need for competition)
- one rabbit hurts the rules (I assume this is the main reason for you, because the submissive rabbit needs to learn again, that the dominant rabbit is not ill anymore)
- dominant rabbit gets ill, submissive rabbits try to rise their rank
- dominant rabbit dies, the others (more than one) need to find a new "leader"
- one rabbit has pain and reacts excessively aggressive (I assume you have them checked by a vet regularly)
- one rabbit became fixed (male or female)
- rabbits were separated for some time (illness, surgery, holidays)
- pair/group of non-fixed males nearly never works
- pair/group of females have a high risk of fighting during puberty (male plus female, one fixed, work best in general)
- young rabbits (1 to 4 years old) have in general more fights than seniors
examples for second floor from kaninchenwiese.de
- experience since nearly 8 years now with rabbits, first pairs, now a group of three.
- kaninchenwiese.de a website in German language, opened 2008, I use since I own rabbits. I trust their detailed information in all topics. They run an emergency-station and a shelter for rabbits and have much experience with very different groups.