Well to solve this question we first need to know the formula for finding simple interest as because you dont state otherwise is what Im going to find for you which is,

S=starting amount, I=interest rate, and T=amount of years that the cash has been in the bank. So now all that we need to do is input are numbers like so 12000(1+.05)

now just solve like so,
12000(1+.05)

=16081 now to find how much she paid extra take,
16081-12000=4081 so are end answer is she paid $4081 in interest.
Enjoy!=)