Triple Trouble by Janet Lambert
The moment Cinda hears that her brother War-Horse and Melody Ayer are planning to elope, she knows that it won't be a dull summer after all. Little did she know that her own romantic difficulties would keep her occupied throughout the summer. Then the Hollister family is thrown into turmoil when Lindsey Hollister announces that he wants to forego college for a career in major league baseball. How will Cinda use her lively personality to see her through the "triple trouble?"