How can she pay for the books using dollars nickels and dimes?

She cannot pay for the books using only dollars, nickels, and dimes. The total cost of the books is $19.75, which is equivalent to 19 dollars and 75 cents. Nickels are worth $0.05 each and dimes are worth $0.10 each. Therefore, it is not possible to make up the exact amount of $19.75 using only dollars, nickels, and dimes.