We were in a similar situation a few years ago. You can only get tax relief against relevant earnings. Yes, she can set up a PRSA, but she'll only get tax relief on the contributions when she returns to work.
Is it possible for an unemployed person to get tax relief on contributions to a PRSA? I know a PRSA can be funded and the contributions carried forward for tax relief later, but is there an opportunity to claim tax relief on contributions of 1,525 per annum, or do you have to have earned income...
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You might be better off maximising your own AVCs now up to age allowed limit, and then maximise your wife's when she returns to work.