A rabbit's growth is part genetics and part environment. If she has been in a clean, healthy environment with adequate nutrition, she must just be genetically smaller than the others.
The only way to "fix" this is to cull (as in remove- not suggesting any particular methods) smaller rabbits from your herd and just work with the larger rabbits who meet the weight requirements for your breed. This assuming you're a breeder? Since you said you wanted to show. If not, it's probably best to sell Nora as (or keep her as) a pet and invest in a larger doe who you'll be able to show.