Never ever let her run out of food or fresh water. And you are going to lose some. If you are in any kind of area with other breeders, and you cannot bring yourself to kill-cull the litter down yourself, you might want to offer 5-7 kits free to anyone who will foster them (on a doe with newborns). It is kinder than letting some starve, and will give them all a better chance.
Supplement: Calf Manna, BOSS, and Old Fashioned Oats. Dandelions are wonderful.
And echoing eco2pia, don't let her run out of food or water.
When my does have large litters, they eat everything I put in their cage.