If she has been working for nearly 4 years, and she has lost a days employment, and is now down to a 3 day week, then she should be able to get Jobsekers Benefit. They work on a 6 day week basis (they don't count Sundays), which means if she is working 3 days, she is considered unemployed for the other 3 days and will get 3/6 of a payment (ie, half). Her rate will depend on her earnings in 2009, if she was earning 300 Euro or more per week in 2009, the full rate is 188, which means she will get 94 Euro/week for her 3 days unemployment each week.
If she was earning less than 300 Euro/week in 2009, she will get a reduced rate. See here for the rates:
http://www.welfare.ie/EN/Publications/sw19/Pages/sw19_sect6.aspx
Also keep in mind that they do not count Sunday in their calculations, so if one of the days she works is a Sunday, then she would actually be considered to be on a 2 day week, and would get 4/6 of a payment.
If she has 260 or more contributions over her working life, her Benefit will last for 312 days. If she continued on a 3 day week, this benefit would last 2 years. If she has less than 260 contributions her Benefit will last 234 days which again if she continued on a 3 day week, would last 18 months. It will obviously run out quicker if she is on a 2 day week or less, as she will exhaust her days entitlement more quickly.
She will also have to be looking for full-time employment to qualify for a payment.