She's always on the go with her busy career, but in April, Christie Brinkley ’s Instagram followers found her in an actual whirl!

The supermodel posted photos of herself twirling onstage with rocker boyfriend John Mellencamp during his concert in Illinois. “Hold on to 16 as long as you can,” Christie wrote, quoting John’s classic song, “Jack & Diane.” And is she ever!

christie brinkley john mellencamp getty images

John and Christie in October 2015.

Since they became a couple last August, Christie, 62, and John, 64, have been acting like teenagers, pals say. “Christie is just a bundle of positive energy, and that rubs off on
John,” a friend tells Closer. And on April 24, in NYC, “they came out of a hotel holding hands and she had her head on his shoulder,” shares an eyewitness. “They looked in love… very happy and affectionate. They certainly turned some heads!”

RELATED: Christie Brinkley Steps Out Looking Happy as Ever With Boyfriend John Mellencamp — See the Pics!

But the devotion is not all a display. Behind closed doors, things are getting more serious for the happy couple. After Christie spent a week with John on his Plain Spoken tour, “he joked with Christie that she needs to tag along when he plays Niagara Falls in October,” says a friend of the rocker’s. “So they can get hitched where everyone else honeymoons!” Joking aside, adds the pal, “There’s no doubt he wants to marry Christie.”

To read the full story on John and Christie, pick up the new issue of Closer Weekly, on newsstands now!