Here's how I think it went down:
When LeChuck says that the Voodoo Lady has manipulated things, he's not lying. She openly admits this. However, I don't think that it's a bad thing. She does say that she's just a player in a bigger thingmabob (or something to that effect) and I feel that she's pretty much like Dr. Manhattan in Watchmen in that she can see through time and she's not good or bad, but she does play a part in what happens. So basically what I'm trying to say is that people are making a mistake when they automatically assume that lying makes her some sort of villain.