As far as i was aware, maternity benefit is to supplement loss of earnings while on maternity leave, if your not in employment then your not earning any money and therefore your not entitled to any. If you were on unemployment it would just continue at the rate you receive as your not expected to work during this time.
If she is still studying, she would not be considered available to work and therefore could not claim Jobseeker's Benefit (unemployment benefit under a new title)
There is another thread on this topic, even though slightly different, there is was stated that
To qualify for Maternity Benefit, you must satisfy one of the following PRSI contribution conditions. You must have:
at least paid 39 PRSI* contributions in the 12-month period before the first day of your maternity leave, or
at least 39 paid PRSI* contributions since first starting work and at least 39 paid or credited PRSI* contributions in the relevant tax year, or in the year following the relevant tax year, or
at least 26 paid PRSI* contributions in the relevant tax year and at least 26 paid PRSI* contributions in the tax year before the relevant tax year.