Her monthly payment was $314.83. Had she continued to pay that amount for the next 6 months, as per the original terms of the loan, she would have paid a total of $314.83 * 6 = $1888.98
After 6 months the balance was $1,840.34 and she pays off the balance and the interest on the 7th month. The interest on $1,840.34 for one month at 9% interest rate is:
Prt = 1840.34 * .09 * 1/12 = $13.80. The interest combined with the principal = $13.80 + $1840.34 = $1854.14
The savings is: $1888.98 - $1854.14 = $34.84