When my does give birth there is usually only a very small amount of blood after they give birth.
"A small amount of blood is normal, as there is blood flowing through the placentas (afterbirths) and as the placenta is torned the blood in the placenta will be released. However, if there is a lot of blood, if the blood flow is pulsing or if there is a steady flow, you should take your rabbit to the vet immediately as there could be a uterine tear that could be life-threatening."
How many kits does she normally have? She could be in labour, just having trouble passing the kits. Only one kit is kind of unusual, most litters are larger then that.
Do you feel babies in her stomach? Look and see if there is one stuck in the birth canal.
I read that If a doe only conceives one or two kits, she will often go well over the normal 31 days gestation. The kits wind up huge, and she has a lot of trouble giving birth to them.