As a sole trader, your wife can make contributions (one-off, regular or both) to either a Personal Pension (aka RAC) or a PRSA, or both. She can get tax relief on contributions up to limits governed by her age.
You should consider your overall financial position as a couple, both now and in retirement before deciding to start making contributions. For example, if your own pension is going to be sufficiently large that as a couple you'll be on the higher rate of tax in retirement, but she'll only receive tax relief at 20% on her contributions on the way in, perhaps a long-term savings plan might be more beneficial.