The sides were deadlocked 7-7 at the break with a converted try apiece. Ireland took the lead in the 22nd minute when second row Sophie Spence crashed over in the corner. Full back Niamh Briggs rifled over an excellent conversion from the touchline.
Wales hit back through full back Rosie Fletcher who scooted over two minutes before halftime. The Wales pack went through the phases with Shona Powell Hughes and Gemma Hallett prominent and the impressive prop Megan York proving a great link between forwards and backs. The move had looked to have broken down, but Fletcher appeared from nowhere and ghosted over to score. Elinor Snowsill slotted the conversion to level the scores as both teams entered the halftime break confident of a victory.
Wales dominated the early exchanges of the second half and camped inside the Irish 22m line but were unable to convert their dominance into points on the board. Twice Wales were over the tryline but twice they were denied by the referee, both for knock-ons.
Caryl James had the home crowd jumping for joy in the 65th minute when she looked to have scored in the corner but Alison Miller had kicked the ball away just as the winger was about to touch down.
Eventually Prosser put Wales in front with her successful penalty four minutes later while Ireland were down to 14 players.
Ireland refused to throw in the towel with Briggs a constant threat with the ball in hand. A green tidal wave swept through the Welsh defence to set up Briggs with her match winning try in the corner.
Wales may have lost but coach Rhys Edwards was putting on a brave face afterwards. "That was the best performance the girls have put in over the past two years. The scrum was dominant and our defence was always in control. It's a real kick in the teeth to lose a game that was there for the taking but we go to France next week knowing that if we repeat today's performance, we've got a great chance of coming away with a positive result."