She would have to check with specific agencies before she left. A lot of people bring their spouses to Ireland, but be prepared to be jobless for a little while while she finds a firm/company which will sponsor her work visa. You are allowed to work here, but getting a work visa can be a little tricky, as companies have to pay a certain fee for each non-EU citizen they hire. But there are quite a few Americans working over here, and if she happens to be in a health field, it'll be easier (although in that case she will have to have the proper qualifications).