Heat 1/4 cup sugar, lemon juice, & 1/4 cup water in a saucepan over medium-high heat, stirring, until the sugar dissolves. Remove from the heat, and stir in the vanilla extract. Let cool. Beat the remaining 1 cup sugar & the cream cheese with a mixer on medium speed until smooth & light. Add the heavy cream & beat on high speed until smooth & the consistency of whipped cream.