Deliver Us from Evie by Marijane Meaker.

In Deliver Us from Evie, fifteen-year-old Parr Burrman’s main concern in life is that his older siblings Doug and Evie will take over the family farm someday so that Parr does not have to. Although Doug has seemed to turn away from farming since going away to college, Evie seems perfectly fine with farming, a life to which she is well suited given her mechanical abilities and her lack of concern with material possessions and social status. Evie’s world is changed, however, when she strikes up a friendship with Patsy Duff, the daughter of the town’s wealthiest and most influential man. Since Patsy is more conventionally feminine and is regarded as the more attractive of the two, Patsy’s parents are quick to accuse Evie of corrupting their daughter, and a great deal of pressure is placed on Evie and her family to stay away from the Duffs. Evie eventually leaves home, going first to St. Louis and then to New York City, so that she and Patsy may pursue their relationship in relative peace.