Jenni Kantanen scored for the Finnish but captain Mukarama Abdulai, Millot Pokuaa and Grace Animah netted for the Black Queens to secure all three points at Estadio Charrua in Montevideo.
The triumph takes the Africans to six points on Group A's table following the 5-0 opening day victory over Uruguay on Tuesday.
Finland, on the other hand, remain without a win after they fell 1-0 to New Zealand on matchday one.
Ghana coach Evans Adotey made just one change to the side that started against Uruguay, bringing on Pokuaa for injured Fuseina Mumuni.
And it was Pokuaa who got the Black Maidens going on the day, netting a fifth minute opener to put her outfit 1-0 up following a defensive mishap on the part of the opposition. She also netted in the first game.
In the 13th minute, Mukarama, who grabbed a hat-trick on matchday one, took her tournament goal tally to four with a header to make the score 2-0.
Finland, however, pulled one back in the 75th minute through Kantanen, who reacted fast to slot in a rebound when goalkeeper Grace Boadu spilled the ball after substitute Vilma Koivisto released long-range thunderbolt.
The goal gingered the Finns, who mounted more pressure on the Ghanaians for the equalizer. Ghana, as it appeared, were deeply rattled by the strike as they struggled to regain control of the game.
The Maidens were on the backfoot until the 86th minute when Animah scored to restore their two-goal cushion.
With goalkeeper Anna Koivunen anticipating a free-kick into the waiting crowd in the box, the winger directed her ball into the net.
The 17-year-old shot-stopper did realize the intent but little too late to control the 'surprise' as she fumbled with her attempted save and broke down into immediate tears after the goal.