Adjouvi Zinsou's two goals allowed her team to move past Group A of the competition taking place at the Stade Yamoussoukro in Cote d'Ivoire.
In a dramatic last 10 minutes, Zinsou scored the game-winning goal to give her team the victory and a spot in the semifinals.
Her goal in the 21st minute, after AS Police had originally resisted their opponents before giving up, marked the beginning of a heartbreaking triumph.
In order to start the scoring, Zinsou took advantage of the friendly defense of the hosts, displaying her strength as she did so.
The Nigeriens had the chance to restore parity on 33 minutes when they had a penalty after an attacker was fouled in the box. It did not materialize as goalkeeper Diane Finagnon saved the resultant penalty kick by Candida Quarshe.
The two sides returned from the break determined to win the match with most of the opportunities coming to AS Police who took the game to their opponents.
They were rewarded for their resilience in the 82nd minute when captain Falmata Mamadou calmly slotted home from a goalmouth melee
The joy of the Nigeriennes was short lived as Zinsou snatched the winner as the referee prepared to blow the final whistle sparking wild jubilation for the Beninoises.
Espoir advance to the semi-final where they will face home side Africa sports on Friday while AS Police are eliminated from the tournament at the group stage just like the previous competition last year.