In a large bowl, mix together yogurt and 1/4 cup of the sugar. Peel mango, remove pit and dice. Set aside 1/3 cup of the diced mango to garnish top of dessert. Fold remaining mango into the yogurt mixture. Set aside.
Place the water in a small dish. Sprinkle gelatin over the top. Let stand 5 minutes to soften. Microwave for 15 seconds until gelatin dissolves completely. Let cool.
Coat the bottom and sides of a 9-inch springform pan with nonstick cooking spray. Line sides and bottom with ladyfinger halves. Reserve any unused ladyfingers for snacking. Set aside.
In another large bowl, beat cream until foamy. Gradually beat in the remaining 1/4 cup sugar until soft peaks form. Beat in vanilla extract, then gelatin mixture. Continue to beat until stiff peaks form.
Fold whipped cream into the yogurt and mango mixture. Spoon mousse into the prepared pan. Cover and refrigerate for at least 4 hours or overnight.
To serve, garnish with reserved mango and lime zest.