Sorry for the long wait. I just logged on and saw this.
Cats can often times go a good 1-2 days between the first stages of labor (losing the mucus plug, nesting) and the second stage of labor when contractions start. Once the contractions start, we want to see a kitten within 1-2 hours. If there are contractions lasting more than 2 hours and no kitten, that is the time to see a vet and consider a c-section if needed.
Between kittens there can be a rest period for 2-4 hours with no contractions. Once the contractions start again, you should see kittens again within that 1-2 hour period.
Most cats have their kittens without issues. Occasionally we will see one where a kitten is stuck and a c-section is needed. Hopefully that doesn't happen with her, but it's something to be ready for just in case.
The day after she has the kittens, it's a good idea to get an exam and make sure all the kittens are out. If there are any retained, then again we should assist in getting them out.
I hope this helps, let me know if you have any other questions.