She applied for unpaid leave (keeping her position) to do graduate studies.
Tips
usage
Most often appears in 留职停薪 (liúzhí tíngxīn, 'keep position, suspend salary') - Chinese HR-speak for unpaid leave where your job is held for you. Compare 离职 (lízhí, to leave the job) and 停职 (tíngzhí, to be suspended).