There were lots of good comments to this email but since the woman did not ask you to reconsider, I'd drop it.
No need beating a dead horse!
If she asks again, I'd just give her a price and only mention the cost of materials, generally speaking, and let it go.
Some people have no clue and don't want to be educated.
There are also those who have no clue about the value of years of experience or training. They don't want to pay for you being smarter or better trained/educated than the next person...