
You will know when your bitch is ready, it's when they flick their tail at any male! Our bitch started showing signs of readiness when one evening she started flicking her tail towards our male dog. The next day she went to the vets for a swab and he said "tomorrow will be your best time"
However why do you want to breed your nervous bitch? Is she nervous for a reason? It could be gentic, if not pups may learn that behaviour in first 8 weeks and you will end up selling nervous puppies to families who then have to spend £100's on behaviourist training to get their pup to walk calmy down the road. Nervousness can easily turn into aggression, either in the pups you sell or worst case sernario your bitch towards her own pups.
As for days, bitches don't read text books :) It will be anywhere from day 1 onwards! Although bitches tend to be quite similar to their mum and liskewise so I would ask the bitches breeder and the grandmothers breeder etc. :)