Ireland had lost their opening three fights at the competition in Hungary but European Youth and Junior champion Moorehouse was in no mood to let that number creep up to four.
The Bray light flyweight dominated Spaniard Marta Lopez in the Last 16 to move within one win of a medal.
Moorehouse had beaten the same opponent on a unanimous decision at the European Youths in April and emerged a split-decision victor here.
Moorehouse, who will remain a Youth boxer next year, will box to guarantee bronze on Sunday afternoon against a soon-to-be-confirmed opponent.
Ireland have two fighters in action tomorrow with Belfast flyweight Caitlin Fryers, a bronze medalit at last year’s championships, boxing Thai fighter Kittiya Nampa in the Last 16 and Tyrone light fly Jude Gallagher, the Irish male captain, facing China’s Renuex Zhao in the Round of 32.
Tuesday August 21st
57kg Dearbhla Rooney (Ireland) lost to Panpatchara Somnuek (Thailand) 2-3
52kg Dean Clancy (Ireland) lost to Asa Stevens (USA) 2-3
Wednesday August 22nd
56kg Brandon McCarthy (Ireland) lost to Akash Kumar (India) 0-5
48kg Daina Moorehouse (Ireland) beat Marta Lopez (Spain) SPLIT
Thursday August 23rd
51kg Caitlin Fryers (Ireland) v Kittiya Nampa (Thailand)
49kg Jude Gallagher (Ireland) v Renuex Zhao (China)
Sunday August 26th
75kg Lauren Kelly (Ireland) v Tallya Brillaux (France)
48kg Daina Moorehouse (Ireland) v TBC
48kg Daina Moorhouse (Enniskerry)
49kg Jude Gallagher (Two Castles)
51kg Caitlin Fryers (Immaculata)
52kg Dean Clancy (Ballinacarrow)
56kg Brandon McCarthy (St Michael’s Athy)
57kg Dearbhla Rooney (Sean McDermott)
75kg Lauren Kelly (St Brigid’s Edenderry)
Team manager: Stephen Connolly and Tara Mari Robins
Head coach: Billy McClean
Coaches: Michael Carruth, Michael Mongan, Anita Just
Physio: David Cooke