How long can my gf stay in the country and what are my options?

My girlfriend is from Brazil. She's here learning English in school and also works as an au pair. I believe she has a visa that allows her to study and work a certain amount of hours per week - but I don't think she can work a full time job. Now she tells me that her visa another 2 years - but I want to find out what happens after that. We may get married at some stage in the future but I want to know what my (her) options are when her visa runs out. I don't want to have to marry her by a specific time - I'd rather do it when the time is right.

Can anyone please tell me what the rules are for people from that part of the world? What about working? Once her English is fluent I would like her to get a proper job - but need to find out what the rules are. She was a nurse back in Brazil - how would I go about seeing if she could get a similar job in Ireland?

Thank you.