After winning no faceoffs in the first quarter, Mullins won 10 to secure the momentum for Penn State.
O'Neill was named the Intercollegiate Women's Lacrosse Coaches Association Offensive Player of the Week and Big Ten Player of the Week.
The Nittany Lions put up a seven-spot in the sixth inning to pull away with the victory.
Gaby Garcia tallied the first grand slam of the season in the mercy-rule win.
Johnson registered an average of 7.6 points, 0.2 assists, and 3.0 rebounds per game through 20 appearances and eight starts.
Nemeth led the blue and white to its first three-game sweep over Indiana since 1999.