Dear Sas,
First of all, we need to know what type of leave that she has apply from oct to dec. Is it anual leave/ unpaid leave etc, and are all this leave is approved with formal form. Ex, she need to apply leave, superior approve and sign the leave form (if she have the hardcopy for evidance is better).
And when she want to resign, did she fill in the resignation form?.. because if she did not fill the form, the emp'er can abscond her because she did not turn to work.