I'm so sorry to hear about the kittens.
You may want to take your cat to the vet if she seems ill. Sometimes kittens die from illnesses that are passed from their mothers.
I'm not sure how long the drying-up period takes. My mother cat had a bad mammary infection, so I can't judge my her experience.
Some of the symptoms she showed were: refusal to nurse, pain when touched, biting, fever, refusal to eat, and weakness. She was put on an antibiotic and I helped her drain her abcessed teat. If one of your cat's teats seems unusually swollen and tender, she might have an infection.