The Águilas opened the scoring in the 29th minute with league-leading goalscorer Lucero Cuevas scoring from inside the box to make it 0-1 for the visitors. Three minutes later, América made it 0-2 as Daniela Espinosa finished off a through-ball to give the Águilas what looked like a comfortable lead.
But Chivas reduced the deficit in the 36th minute, when Tania Morales pounced on a rbeound given up by goalkeeper Aurora Santiago to make it 1-2.
In the second half, the Chivas comeback continued. In the 68th minute, Arlett Tovar tied the game 2-2 when she headed home a corner kick.
Then, Morales scored her second goal of the night, and a truly spectacular one, when she made it 3-2 in the 81st minute with an Olympico.
Chivas then gave themselves a two-goal cushion to take into the second leg when Daniela Carrandi scored in stoppage time to make it 4-2.
The return leg will be played next Saturday, the 11th, at América. There is no away-goal tiebreaker in the Femenil semifinals, meaning that América will need a three-goal victory to win the series outright, and a two-goal victory to send the game to penalties. Chivas would advance to the final with a win, a draw, or a one-goal loss.