Griffith landed on the ground and stayed there until paramedics came and treated her for what Cypress Coach Nicole Woiemberghe said appeared to be a "head contusion."
Once the medics treated Griffith and took her to a nearby hospital, the officials huddled together and awarded Cypress (17-8) with a penalty shot and Cousineau a yellow card. With Cousineau forced to sit out the penalty kick and reserve goalkeeper Samantha Harper suddenly called on to keep Flintridge Prep's season alive, Cypress' Sam Rice fired a shot over the crossbar to keep the match knotted at 1.
"[The referee] called a foul on their player and then he changed his mind," said Flintridge Prep Coach Esteban Chavez, whose team will face top-seeded Ayala or Lakewood St. Joseph in a quarterfinal road game at 3 p.m. Thursday. "I can understand if he made a mistake.
"We were tested by a good team. We scored in the first half and we created a lot of opportunities."
Woiemberghe, who piloted Cypress to the Empire League crown, said she was confused as to what the officials might call.
"The ball dropped and the goalie's hand hit [Griffith's] head," Woiemberghe said. "I was talking to the referee and I thought it might be a penalty kick, but I wasn't counting on it, though I knew it would be a possibility.
"We knew it would be a physical game. We didn't have possession as much as we would have liked."
The Rebels, who won the Prep League championship before beginning the playoffs with a 3-1 victory against visiting Diamond Bar on Thursday, got a nice corner kick from the University of North Carolina-bound Elby that was headed in by Kelleher in the 54th minute.
The Rebels then held off several late comeback bids by Cypress, including one point-blank shot apiece from Alexia Morales and Emma Pridmore in the final 10 minutes.
Flintridge Prep opened the scoring in the 15th minute. Flintridge Prep junior midfielder Connell Studenmund crossed a pass to Elby, who gained control of the ball and lined a shot past Cypress senior goalkeeper Amy Fisher.
Cypress knotted the match at 1 with a minute to play in the first half. Rice made a pass to Pridmore, who beat Cousineau on a low shot.
Elby, a reigning All-Area first-team honoree, said the Rebels were able to regain their focus after Cypress' goal.
"Actually for us, it was déjà vu just like Thursday," said Elby in reference to her team's first-round win in which a Diamond Bar player suffered an apparent neck injury and was taken away by emergency personnel. "A girl gets hurt and the ambulance comes.
"We realized that we had to get our game together and regroup."
Cousineau finished with 12 saves.