Before the peach and the insects got bigger, Miss Spider is first seen as a normal-sized spider in James' window. He befriends her and rescues her from his horrible aunts the next morning.
She was one of the insects in the fruit after eating the magic Croccodile tongues. She is a mother figure to James in the film version. While in the book, it's Ms. Ladybug who takes on that role. In the end of the film, It is revealed that she is the owner of "Spider Club" in Central Park, New York.