Joy, Aranea and Nellie were three of Charlotte's 514 children. They are mentioned at the end of the book. In "Miracles do happen", a second "Charlotte's Web" novel, Nellie has been separated from her sisters Aranea and Joy and becomes the new Charlotte for Wilbur, writing various words in her webs from various visions given from Charlotte's spirit. She was burned by a forest fire and had a near-death experience where Charlotte's spirit gives Nellie a loving, comforting hug as her distraught daughter cries and hugs her mom, before thrusting her daughter back to life to aid Wilbur on his new mission.
They are seen at the end of the film. In "Miracles do happen", Nellie has been separated from her sisters Joy and Aranea and must follow Charlotte's ghost to find Easter's Eye and deliver it to Fern Arable. Nellie is condemned to die like Charlotte before winter, but Easter's Eye performs a miracle which increases her lifespan for a while longer until Wilbur's mission is complete. At the end of the film, thanks to Wilbur's selfless sacrifice, Nellie is blessed by Easter's Eye to outlive Charlotte many times to see and raise her children as a true mother, while Joy and Aranea return to Maine and die after making their egg sacs.
In the 1973 film, all three of them have the same appearance. In the 2003 sequel, they are given different hairstyles. Nellie has red hair, Joy has purple hair, and Aranea has gold hair in three pigtails. But In the original movie, they don't have any hair and look like there mother. Charlotte.