Riding her French stallion, Mylord Carthago HN, the 32-year-old helped France to their first Nations Cup victory since 2009.
"This victory warms up our hearts. The horses seemed all in good shape. After a difficult beginning this season, this victory is just what we needed," Leprevost said.
France face some selection worries ahead of the Olympics, after a sudden injury to Orient Express HDC ahead of the Nations Cup put Patrice Delaveau's participation in doubt.
The definitive French squad is expected to be announced on Monday.