As the Un-Rules Manager (I got the job because I was the only one willing to do it), let me walk you through what happens. Your Pollenbright Winged Little Girl deals ½ damage to your opponent. Pollenbright Wings then puts half of a 1/1 green Saproling into play. For most purposes this makes it act like a ½ / ½. For example, if you deal damage with half of a Saproling token, it deals ½ damage. If your half of a Saproling token is Swords to Plowshared, you get half of 1 life, a.k.a. ½. The only difference is the token is half a creature. You cannot sacrifice it to a cost that requires sacrificing a whole creature such as Goblin Bombardment. You can, though, sacrifice two half tokens to get one activation of Goblin Bombardment.