What to do about a late litter?

First I'd better explain this complicated situation.

I bred my Dutch doe, Rosemary, on September 14. However, about 10 days later, she began to exhibit all the signs of a false pregnancy. She pulled fur, made haystaches, and made a tidy little nest. The other times I bred her she made a nest at the very last minute before she kindled, so I was sure that the breeding was unsuccesful and she wasn't just making a very early nest. So I rebred her on October 3. Unfortunately, it turned out that the breeding was succesful and she WAS pregnant. On October 16, she kindled from the first breeding and had three large kits. Unfortunately the biggest one died. So, for a time, she had two litters developing in her and I hope that didn't mess anything up. The litter from the second breeding was due November 2 (day 30), but she still hasn't kindled. She is obviously very pregnant, and though I can't palpate for the life of me, it is very obvious that she has an unusually large litter inside. Rosemary has always been very prompt with her litters, kindling on day 30, so I really think that something has gone wrong. She also hasn't started nesting yet.

I am, to say the least, very concerned for Rosemary. Are there any herbs I should give her? Should I take her in to the vet for an ultrasound/c-section? (though I would like to avoid that if possible). Are late litters like this fatal? Thanks for any info!

I would first make sure she really is pregnant.
Carrying two litters at once is possible, but in practice is extremely rare, most breeders never encounter it. If it were more common, it would be happening all the time in cases where "We were told they were both females!" with a buck and doe living together.

There are several reasons why it doesn't happen often. Like most mammals that have litters - rather than single or twin offspring - rabbits have two horns to the uterus which provides a greater internal surface area for all the embryos to attach. In the rabbit, each horn has a separate cervix. This means that, in theory, a rabbit could carry a separate litter in each horn, but in practice this rarely happens as both ovaries shed eggs into the fallopian tubes during ovulation, with some ending up in each horn. If a horn contained embryos of mixed ages, both would be expelled during the strong contractions of labour.

She is definitely pregnant. Though I'm awful at palpating and therefore can't feel any babies, she is very big and it's not fat or fur. She has also been acting very frenzied lately, and eating and drinking a lot. Thank you for the reply, though!

Honestly, under normal circumstances I would not think she's pregnant. Pregnancy isn't really determined by mating, but hormons. I've heard of litters days apart, does happen, but I would rather suspect differences in nutrition supply to the uterine horns than a double pregnancy. Had a litter with all kind of devlopent stages, non viable, but there sure can be problems in that regard. If it just effects one uterine horn you might get litters some time apart.

Would be nice to hear of someone breeding a doe with diferent bucks, days apart, and getting 2 seperate litters attributable to each buck.

Nursing does can get big because of eating A LOT, that stuff doesn't pass through quicker but imo does fill them up.

So, I would just wait and see, give her all the hay she wants. Day 30 would be quite early for mine, normal for them is 32-35.