PRSI is calculated on a week-by-week basis so unless the employer used an incorrect PRSI class (the class is determined by earnings each week) it would seem unlikely that she has anything to reclaim.
As a guide, in 2019 class A0 would apply to weekly earnings between €38 and €352; AX would apply to weekly earnings between €352.01 and €386; AL would apply to weekly earnings A1 between €386.01 and €424; A1 would apply in all other cases. You can use this to check if the correct PRSI class was used in individual payslips.
Total USC payable on annual earnings of €15000 should amount to €120. If her total USC deductions exceed that she should be due a refund of any excess.