The 24-year-old began 2018 on a high, providing two assists and one goal to power Sarah M'Barek's ladies into the round of 16 stage of the competition on Sunday.
Faustine Robert and Marine Pervier set the stage rolling for the visitors with a goal apiece in the opening 10 minutes.
In the second half, Lea Abadou added the third before Robert got her second of the encounter, then Oparanozie weighed in the fifth past the Arlacaises.
The ruthless Guingamp side remained unstoppable as Louise Fleury, Robert with her hat-trick plus Ines Ou Mahi's strike completed the riot for French top-flight club.
Oparanozie has now scored three goals in 13 appearances in all competitions this season for the Saint-Brieuc outfit and they will resume their league campaign against Rodez on January 14.