Despite only entering the field at half-time, Brown proved to be the game changer for Crystal Palace.
The Eagles went into the break level with Portsmouth knowing that a win would guarantee automatic promotion.
Manager Jo Potter opted to bring Brown on at half-time, a decision that helped Palace earn their place in the topflight.
Ashleigh Weerden fired Palace ahead on the 47th minute, courtesy of an incisive pass from Brown.
Just eight minutes later and Brown did the same again, this time cutting back inside and lofting a perfect pass to Weerden at the back post - who finished superbly.
Then, on 69 minutes, with Palace 5-1 up - Brown bagged her third assist of the game.
A quick exchange with Weerden on the left-wing saw Brown cut onto her weaker right foot and pick out a beautiful cross to Elise Hughes, who nodded past the Portsmouth 'keeper.
It was a stunning performance from the 18-year-old, as her three assists helped Palace to a 6-1 win and a place in the WSL next season.
Brown was the standout pick with 45.8% of the vote, with Weerden in second-place with 27.8%.
Rounding out the top three was goalscorer Annabel Blanchard - who got 13.2% of the vote.
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