When I was a kid I read a book called A Royal Pain by Ellen Conford. It was about a fifteen-year-old American girl, Abby Adams, whose family is approached by delegates from a (fictional) small European country called Saxony-Coburg, where Abby was born while her parents were on vacation there. The delegates claim that recent deathbed testimony by a maternity nurse has revealed that Abby was switched at birth with the princess of Saxony-Coburg, and request that she return to Saxony-Coburg with them to assume her duties as royal heir.
(There is no mention at this point of the other girl, with whom she was switched and who until now has believed herself to be the crown princess. The delegates have not brought her back to exchange. The Adamses do not ask about her.)
Abby is nervous but excited to go to Saxony-Coburg and become the princess. When she gets there, via helicopter, everything is weird and old-fashioned and she wishes she spoke better French, but she's having a pretty good time until she discovers that she is officially betrothed to Prince Casimir of Arcania, whom she does not like because he looks like Anthony Perkins from Psycho and his hobby is taxidermy. Also, she has fallen in love with a hot young newspaper reporter who came to interview her on her arrival in the country, so you can see why she doesn't want to marry Casimir, which she is scheduled to do in like five days from now, on her sixteenth birthday.
Additionally, Dolores, the previous princess, just wanders sullenly around the castle now, talking to a stuffed Snoopy dog about how her heart is broken because she is in love with Casimir and will now never get to marry him.
(Casimir has not demonstrated a matching attitude. He seems very stoked to marry Abby. There are multiple scenes, played for comedy, in which he is trying to kiss or otherwise embrace her and she is literally physically running and hiding from him and, in one case, calling her dog to protect her.)
Abby and Dolores eventually team up to help her escape, and there's a scene involving the national gloxinia festival and a jeep and cross-country skis, again played for comedy, and eventually it's revealed that the nurse's deathbed confession was a lie, and Dolores marries Casimir and Abby goes home and takes her midterms.
It was written in 1986. So that's what 1986 was like.