The Watchdog — LaJoyce Martin

At seventeen, wealthy Trinna Clovis is tired of the watchdog her father has hired to safeguard her. He follows her everywhere! When she meets Abby, a poor farmer's daughter, on the train, they decide to exchange clothes to fool the guard. And they succeed. But the maelstrom they build for themselves is more than they bargained for. How will they ever clear up the confusion? A disappointed boyfriend, doubting parents, and a discerning grandmother all play a part in the final outcome.