This book is by Maud Hart Lovelace, and it is about one of Betsy, Tacy, and Tib's friends: Winona Root.
Winona's 8th birthday is coming up and she is going to have a party. Her father,who is the editor of the newspaper, prints out 15 invatations. Her mother addresses them all to her friend's children, and other children that Winona is friends with(or she thinks Winona is friends with). But Winona wanted to invite other children, so she just tells them at school. But her main concern is what she wants for her birthday. Winona wants a pony really bad, so she told everybody that she is getting one. But as the day draws near, she is not so sure. What if she didn't get a pony for her birthday? She has lots of fun at her party, and then came her heart's desire. A man came out of the stables leading a pony harnessed to a cart! All the children have fun riding in the cart, and when they left, Winona went out to see her pony. But he is not there! She ran out of the stables, only to see the man leading away the pony! He told her that his bussiness was to go and give children rides on the pony, and now he was going to another town. Winona was heartbroken, but soon recovered. Her parents have a discussion and decide to buy the pony. Winona learned how to take care of him, and also learned a lesson on growing up.
