Dikwena did well come from behind after Ea Lla Koto grabbed the lead through a long-range strike from Sello Nephali in the 29th minute, but the Rustenburg-side took just six minutes to find the equaliser through Sabelo Tsambo, thanks to a well-taken left-footed shot from just outside the box.
The two sides went into the break deadlocked at 1-1, but Platinum Stars came out guns blazing in the second and took the lead three minutes in, courtesy of Kobamelo Kodisang.
Free State Stars could do little to come back from the deficit and allowed Platinum Stars a third-place finish in Group B to ensure a spot in the quarter-finals alongside Mamelodi Sundowns, Orlando Pirates and Mpumalanga Black Aces from Group B.