SOLVED. Children's book with one of the two main characters being named Courtney [s]

[bookel]

Maybe this?

The Kidnapping of Courtney Van Allen & What's-her-name by Joyce Cool
When 12-year-old Jan Travis is kidnapped along with her world-famous, wealthy friend, the kidnappers demand something other than money.

[SparksofEmber]

Kidnapping of Courtney Van Allen & What's-her-name for the link.

[SparksofEmber]

Maybe Gemma "Accustomed to a glamorous life as a famous young movie star, eleven-year-old Gemma is horrified when, because of her mother's film career, she is sent to live with her "dull" and unknown cousins in a small industrial town."

[Juels]

Could it be the My Crazy Cousin Courtney series by Judi Miller?

My Crazy Cousin Courtney
My Crazy Cousin Courtney Returns Again
My Crazy Cousin Courtney Comes Back
My Crazy Cousin Courtney Gets Crazier

[Juels]

You're welcome.