You should never breed an animal that has an allergy or any other health-problem that has become manifest. Only healthy fit animals should be bred, not just to get offspring with the best possible genes, but also because pregnancy is very tough on the body and and a sick bunny is less likely to be able to nurse and care for her young let alone survive.
That said, we don’t discuss intentional breeding of rabbits here. We feel that there already are so many rabbits in this world that don’t have good, loving homes, and we don’t want to add to this problem by promoting breeding. (I’m not saying that you personally wouldn’t take good care of your rabbits).
I think you should take your bun to a vet if she keeps sneezing and has a runny nose. She may need antibiotics. If it’s an allergy you need to find out what it is she’s reacting to – litter, type of hay (some buns are actually allergic to timothy hay), the pellets, certain greens, pollen, other pets etc.