Van Dike's goal came just one minute after Pella's Brenna Boat tied the score. Van Dike scored on a Rachel Morrissey cross to push the Warriors into the Class 1A semifinals.
Norwalk's first goal came just four minutes before the end of the first half as Mallory Risbeck scored on a Krista Obley assist.
The Warriors controlled the action for much of the match but strong play by Pella's all-state goal keeper Tremaine Versteeg kept the match close.
Norwalk improves to 17-4 and will face 12th-ranked Waterloo Columbus/Don Bosco in the Class 1A semifinals at 11 a.m. Saturday.
Pella ends its season at 15-4.
Norwalk 2, Pella 1
Pella 0 1 -- 1
Norwalk 1 1 -- 2
Scoring:
N: Mallory Risbeck (Krista Obley), 36:00
P: Brenna Boat, 75:00
N: Julie Van Dike (Rachel Morrissey), 76:00