Newly adopted teenager faking chest pains

We recently, (very recently, in the past two weeks) adopted two teenagers from west Africa. We had been trying for almost 8 years. Today they both started school our oldest, who is 17, did not like school and started faking chest pains on the way home in the car when I told her she had to go back tomorrow. We had her medically checked and she is just fine. Physically. Any advice on how to handle?