Just quickly, if you plan to breed her again in the future, I would take her to the vet now.
She may have some remaining tissues from the pregnancy that, if left to rot and cause infection etc etc, could make her barren.
Not sure if there is a rabbit equivalent to a human D&C (where they scrape out your womb after a miscarriage), but she may need something similar.
Vitamen C wont be doing anything if she has an infection.