Hayden Panetierre All Smiles After Revealing Friend's Name Involved in Yacht Incident

Hayden Panettiere is clearly feeling real good about finally spilling it all in her new memoir -- ’cause the actress was all smiles during a recent airport run-in.

Check out the clip -- Hayden was rolling through LaGuardia Airport Wednesday morning with a friend when she got hit with questions about the juicy bombshells in her memoir, "This Is Me: A Reckoning."

The actress was asked point-blank about the mystery pal “Stella” she claims pushed her into bed with a shirtless male celeb on a yacht ... and also about her wild confession involving shrooms while filming "Scream 4."

But Hayden mostly kept quiet through it all -- no big reveals, no denials ... just one very telling grin plastered across her face the entire time.