Hayden Panettiere (a.k.a. the new Julia Roberts) turned vicious with reporters on a red carpet in Hawaii over the weekend.

Look out, folks. Now that she’s no longer with Milo Ventimiglia, Hayden can let her witch flag fly and not pretend to be mature and sweet anymore. Not that we were fooled.

Or maybe she was just having a very bad day. In Hawaii. On a free trip.

According to Us Magazine, the 19-year-old "Heroes" hottie was "testy" when she walked the red carpet at a charity fundraiser benefiting the Rehabilitation Hospital of the Pacific Foundation on Sunday in Honolulu.

"Back up!" she screamed at photogs. Good grief, what a girl has to endure for a free trip to Hawaii!

After posing for photos, she blew by reporters. A female reporter tapped her shoulder and asked politely, "May we talk with you, Hayden?" The actress jerked around and screamed, "Don’t you ever touch me!"

According to Us, she then icily asked a red carpet handler, "Oh, am I supposed to do interviews?"

Approaching media outlets, she gave them the deep freeze — "You all make my life miserable" — and refused to answer questions.

After the red carpet, Panettiere hung out in a private cabana with her new "friend" Justin Long. She then moved to a private dining room, where she and Long sat across from each other, chatting for an hour.

Justin, be careful.

If you thought Drew Barrymore was the Queen of the Unpredictability, wait until you get a dose of Miss Major Mood Swings Panettierre.

Hayden also hid from photogs – under her hoodie – when she was spotted at LAX, returning from Hawaii with "Days of Our Lives" hunk Darin Brooks, who was also at the fund-raising grand reopening of the Royal Hawaiian Hotel. They could have just been on the same plane. No, really.

We’ve heard some unreal stories from fashion folks who have worked with this little lady and quit because of her foot-stomping diva behaviors.

Trust me, it ain’t pretty.

Related Hayden Panettierre, Justin Long posts:

Don’t change clothes at Hayden Panettiere’s house!

Hayden Panettiere’s dad arrested on suspicion of abuse

Are Hayden Panettiere and Milo Ventimiglia getting hitched?

Read more "Heroes" news at Showtracker!

Drew Barrymore caught snogging Chuck Bass! Don’t tell B

Justin Long, Drew Barrymore split? What the?

Photo: Hayden Panettierre and Justin Long at a party early this year. New friends? Hmmm. WireImage

Posted by:Elizabeth Snead