A Dream for Susan by Janet Lambert (1954)
But there's much to be said about wanting something badly enough. And when a girl has a twin brother like Neal and an older sister like Alice, she can't feel miserable and homeless for very long.
First, Neal has a wonderful idea to be followed by an even better one from none other than Tippy Parrish's mother. With the whole Parrish clan joining forces with the Jordons to help Susan realize her dream, she soon finds herself with a home, a family, and a very ardent admirer.
Janet Lambert has a very special touch when it comes to the people she loves. Her books are chock-full of wonderful, fun-loving, very-much-alive young people, and Susan Jordon is one of the most charming and lovable of them all. (from the inside flap)