Gagamel wanted to eat the Smurfs. And in his attempt he made Smurfet to try and trick the Smurfs into his castle so he could eat them, but the over all goodness of the Smurf's village turned her good as well. Smurfs don't reproducer they just are did you ever see a baby Smurf. No because there never was one. They were made by some kind of magic.... The only thing I never really got was if the dude could make Smurfs why didn't he just make more to eat?

Edit: Oh yah and I Smurfed her in the Smurfin parking lot.