I am looking for a mysterious children’s book from what I am guessing is the late 1960s. It was hardbound, unusually tall and narrow, and illustrated in a sort of kooky 60s style. It was about a little girl who lived in the city and whose birthday is right around the corner, deep in winter. Somehow, a wealthy eccentric woman who lives nearby has the same birthday, and decides to invite the little girl over for a special fantasy day. I remember that the woman sends over a dress and coat the day before–– I want to say it was a blue dress with a blue satin sash– so the little girl will have something lovely to wear when she comes. On the day itself, a special coach arrives to pick her up and take her to the woman’s house, and she goes over there, And she and the woman and have a madcap day. I feel like I remember an illustration of a room filled with books, and perhaps a hammock strung up in it. Very Bohemian but very ritzy. I can’t really remember anything more except for the fact that a cat has kittens at the end of the story.