Congrats on the successful dating! I’m by no means an expert (I only have a singleton) but I think you should go with what is best for Nibbles and your family. Does she seem lonely? Do you have time to dedicate to the bonding process, which can take weeks in some cases? These questions are important, as well as the additional cost of food and veterinary care.
That said, I have a single bachelor who I was considering bonding. But he seems happy and healthy with my companionship so I’ve decided not to. I think pairs are great in certain situations so only you can decide whether it is the right time to take on another bun. I’ve heard bonding males with females can be easier (provided they are both fixed) but would go with the rabbit that seems to get along with yours the best. I would ask the refuge if they would allow multiple dates with the same rabbit so you can test the relationship and see if it will work out long-term (rather than commit to taking one home immediately).
Others on her are much more experience and knowledgeable–good luck!