In a large bowl, toss the blueberries and cherries with the brown sugar sweetener. Set aside.
In a small bowl, mix the yogurt, granulated sugar free sweetener, and vanilla extract until well combined.
Place ¼ cup of the berry mixture, with some of the juices from the berries, in the bottom of the trifle bowl. Top with 2 tablespoons of the yogurt mixture. Add ⅓ of the ladyfingers over top of the yogurt.
Repeat layers, topping with the remaining yogurt. Cover and refrigerate up to 12 hours.
Prior to serving, sprinkle each parfait with 1 teaspoon pecan pieces (if using).
WW Points are calculated with the most recent WW Calculator as of 2/22/22