Dogs are pregnant an average of 63 days, or 9 weeks, give or take a day or 2. You can confirm a pregnancy via ultrasound at around 25 days gestation at the earliest, and pups will show up on an x-ray at around 42 to 47 days (because that is when their skeletons have mineralized enough to be seen on an x-ray - but usually it's more obvious the dog is pregnant before that). So it really depends on when exactly in March she is saying the dog is "due" - are we talking March 1st, March 31st, or anytime in between? And what day (or days) was the dog bred? Because it's about 2 months from that day that you can expect her to have puppies.
Some breeders are better than others. Some are very knowledgable and responsible, and others are no more than "backyard breeders" or "hobby breeders" that have zero experience. A breeder can be someone who has been breeding for 30 years with many champion show dogs under their belt, or someone who just decided to let their dog get knocked up by another dog. Either way, I've found breeders to be a quirky bunch and some have very old-fashioned or outdated ideas about dog breeding and dog health in general.
If you are not happy with the communication between you and this person, and you are getting some bad feelings, or feel like she is rubbing you the wrong way, ask for your deposit back and walk away. The simple answer to finding dog breeders is to attend a dog show when there in one in your area. But the other route to consider would be to go through a dog rescue that places animals that already need homes, or your local animal shelter.