So, my first pair was very one sided grooming and was a very strong bond. But, they were very very comfortable around each other, no hints of nervousness from either rabbit, even if one moved suddenly or got very close.
So, I would want to see Lola not be nervous around Jay before moving on. Even if Jay does all the grooming, they should both be very very relaxed around each other. And you should see snuggling. It’s hard to describe, but if you aren’t sure, don’t move on yet. When they are ready, you will know! It’s like something clicks.
It does sound like they are close, but not ready to move to semi-neutral yet. I think a long session sounds like a good plan.
For a long session I would but both boxes in, side by side. Clean them as well as possible with vinegar. Ideally you would use new ones, but if you clean them well it should be ok. Litter boxes can cause some disputes, so be prepared once you put them in!
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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.