The interest for the second month will be $4.5675 or $4.57
Unpaid balance is $300
Interest rate per month is 1 1/2% or 1.5% or 0.015
First month: $300 * 1.5% = $4.50 - interest on the first month.
Since she did not pay for 2 months, the interest charged to her account in the first month will be added to her unpaid balance increasing it to $304.50. This will be the basis of the second months' interest charge.
Second month: $304.50 * 1.5% = $4.5675 or rounded off to $4.57
Total interest charged for the unpaid balance of $300 is $9.07 (4.5 + 4.57)