That's wonderful! Maybe if she has a smaller litter you can foster some from the large litter to even it out some (if they are close to the same kindle date)
Rabbits dont "lay" with their babies like dogs and cats do. They only feed once or twice a day, so it isnt unusual to not see her in the nestbox very often. I would check for full tummies once in the morning, and once at night. You should be able to figure out her feeding schedule quickly by...