Openside flanker Jamie Kift has been handed her first start of the campaign after recovering from injury and coming off the bench against Italy, Catrina Nicholas moving to the blindside; Rachel Taylor replaces the injured Gemma Hallett in the second row and Louise Horgan starts at loosehead with Jenny Davies moving to the tighthead.
Wales Women head to Dublin with two wins under their belt after losing to England on the opening weekend of the Championship. They secured home victories over Scotland 23-6 and Italy 27-5 but this weekend's match in Ireland will be a key indicator of the side's mettle, according to Lewis.
He said: "This is the critical game for us. Our final game against France will be irrelevant if we lose this one give what we've achieved to date.
Both Ireland and ourselves have won two, lost one so far this season so it is crunch time for both sides.
"We have won our last two encounters against Ireland but they were narrow victories and Ireland are an improving side so there will be no complacency and I imagine it will be a very competitive match. It will certainly be a defining game for our Six Nations campaign."
Wales Women v Ireland (Friday 7 March, 7.30pm, St Marys, Dublin):
Non Evans (Clifton); Louise Rickard (Woodbridge), Naomi Thomas (Clifton), Clare Flowers (Clifton), Hayley Baxter (Cardiff Quins); Rachel Poolman (UWIC), Amy Day (UWIC); Louise Horgan (Saracens), Rhian Bowden (Clifton), Jenny Davies (Waterloo), Rachel Taylor (Cardiff Quins), Claire Donovan (Saracens), Catrina Nicholas (Bath Ladies), Jamie Kift (Clifton), Mel Berry (capt, Clifton)
Replacements: Claire Horgan (Lichfield), Ruth Evans (Waterloo), Nicola Evans (Wasps), Jenny Doyle (Bath Ladies), Laura Prosser (Pontyclun), Bethan Walsh (Wasps), Michaela Reed (Birchgrove)