This thought stuck with me for a while and the more I thought about it the more it made sence to me! Charlotte, the spider, is kind of like Jesus. She is working behind the scenes making Wilber out to be the mircilous pig everyone thinks that he is. She never asks for thanks and keeps on doing her "work" to conform Wilber into this great pig. In the end Wilber is spared from becoming the Christmas ham and she dies.
It makes me think of an old song, What a friend we have in Jesus. Here are the lyrics: