Combine low-fat ice cream, peaches, amaretto, and vanilla in a freezer-safe container; stir well. Freeze until firm.
Place thawed raspberries, sugar, and liqueur in a blender, and process until smooth. Press the raspberry mixture through a sieve, reserving puree; discard seeds. Cover and chill.
Spoon 2 teaspoons raspberry puree into each of 8 parfait glasses or champagne flutes. Top each with about 1 1/2 tablespoons of fresh raspberries and 1/4 cup ice-cream mixture. Repeat layers, ending with 2 teaspoons raspberry puree. Garnish with peach slices, if desired.