Katharine McPhee jokes she’s shipping fiance David Foster’s daughters to Switzerland

Katharine McPhee is having some fun with her future step-daughters!

The 34-year-old actress and singer is currently on vacation in Canada with her fiance, David Foster, and while she’s there, she’s also very publicly teased Foster’s daughter Erin, 36, on Instagram.

McPhee posted a pic of herself rocking a sweatshirt and what appears to be a life jacket, captioning the photo, “It’s called fashion sweetie, look it up.”

Erin originally commented on the image, “CHIC,” but when one commenter asked her how awkward it is to have her father marrying a woman younger than her, she started throwing around some jokes.

“I’ve started saying I’m 31, so now she’s 3 years older than me. Im a problem solver,” Erin wrote.

This didn’t sit well with McPhee who replied, “@erinfoster stop blowing my age cover! The day we say I do, I’m shipping you and your sister off to switzerland.”

The comment was a clear reference to the 1998 Parent Trap reboot starring Lindsay Lohan in which the evil Meredith Blake (Elaine Hendrix) threatens to ship Hallie and Annie Parker to boarding school in Switzerland.

Erin quickly got the reference, replying, “@katharinemcphee omg you’re gonna parent trap us!!! I knew it.”

It’s clear the family likes to have fun together and aren’t afraid to address the extreme age difference between the 68-year-old David and his future bride.

Earlier this week, McPhee joked with Erin yet again, teasing, “Mommy and daddy need alone time,” after Erin asked why she wasn’t invited on the couple’s trip.