If your wife has sufficient PRSI contributions to qualify for full-rate Illness Benefit in her own right, then she will get the Personal Rate (currently 197.80). Any payment you were receiving for her will cease (if she was in full-time employment, you may not have received anything for her). If there are children, payments would generally be divided between both claims.
If your wife was in part-time employment, she may not qualify for full-rate IB, but may qualify for Graduated Rate instead.