LINDSAY LOHAN: HOLLYWOOD’S BIGGEST BRAT

“MEAN GIRLS” star Lindsay Lohan is a mean girl!

That’s the inside word from sources close to the just-turned-18 actress, who’s so red-hot she’s now commanding $7.5 million a movie — and is quickly gaining Britney Spears-like status with her wild shenanigans.

“Lindsay can be a real nasty piece of work — a spoiled, jealous and at times vicious brat,” an insider told The ENQUIRER.

UNDERAGE BOOZING

Lindsay spends most of her spare time with her 24-year-old boyfriend, “That ’70s Show” star Wilmer Valderrama, and hanging out in over-21 clubs — where she routinely engages in underage drinking, sources say.

“Lindsay parties like there’s no tomorrow — she even had her 18th birthday party at an over-21 club,” the insider disclosed.

“Lindsay drinks alcohol — she doesn’t care that she’s underage. And alcohol doesn’t improve her temperament, it only makes her more belligerent!”

At one of Lindsay’s favorite Los Angeles restaurants, Koi, “the service staff hates to wait on her because she’s such an obnoxious little monster — but it also gives us something to laugh at after she leaves,” said a source at the ‘mean girls’ star eatery. “Lindsay’s only 18 so we won’t serve her alcohol, yet she always puts up a fight.

“‘I asked for a drink! And bring my friends drinks too!’ she recently yelled at a waiter, and wouldn’t let up.

“While Lindsay was carrying on, other diners couldn’t help but notice her. Finally Lindsay turned to some middle-aged men at another table and said, ‘What’s wrong with you? Haven’t you ever seen a celebrity before?’

“The guys just rolled their eyes. “Later, they picked up the bill for Lindsay’s table and left her a note saying, ‘Use the money you just saved on dinner to buy some charm lessons. You certainly need some.’

“A few days later, Lindsay went back to Koi with a stack of photos of herself, and was standing at the door offering to sign them for people. But no one really wanted one — people go to Koi to eat, not to attend a Lindsay Lohan fan club meeting!”

MAKING ENEMIES

An industry source revealed to The ENQUIRER: “Lindsay is alienating people at a record pace — even the people who are supposed to be her friends.

“She’s managed to make enemies of her former close pal Tara Reid, talking badly about her behind her back. Tara finally had enough and went directly to Lindsay to have it out.

“Lindsay screamed at her, ‘You’re a has-been! You’re so over it’s not even funny!'”

EGO PROBLEM

And as The ENQUIRER reported recently the two nearly came to blows in Las Vegas and had to be separated.

“Lindsay’s also at odds with another close friend, ‘The O.C.’ star Mischa Barton, because Lindsay badmouthed her,” said the industry source.

“‘Mischa’s TV and I’m movies,’ Lindsay boasted to some pals. ‘Everyone knows I’m the bigger star.’

“Now she and Mischa are barely talking.”

JEALOUSY

A friend of Lindsay told The ENQUIRER: “Lindsay is getting worse as her ego gets bigger.

“One time Lindsay was raging at Wilmer, insisting he had too many women around him and was too nice to them. Then when he wasn’t looking, she took his cell phone and erased all the girls’ phone numbers he had saved!”

Teen “It Girl” Lindsay got her first big break playing twins in “The Parent Trap” when she was just 11, and last year’s “Freaky Friday” set her on the track toward stardom.

At the 2004 Teen Choice Awards she picked up four awards — and for her upcoming movie “Lady Luck,” she’ll earn more than $7 million.

But an ex-friend told The ENQUIRER: “I don’t think Lindsay has become a nasty person just because she’s so successful. I think she’s always been that way!”

FAN ABUSE

The ego-bloated teen has even been mean to some of the adoring fans who flock to her movies. A few weeks ago The ENQUIRER revealed that Lindsay made two kindergarten-age girls cry when they tried to approach her in a restaurant — telling the waitress to keep them away from her table. And Lindsay blew off an admiring fan at Las Vegas’ Palms Casino Hotel recently when she was asked to pose for a photo.

Lindsay was exiting a party with a drink in her hand when she reportedly railed at a startled fan, “Get away or I’ll kick your ass right here.”

Another ugly incident involving Lindsay’s fans came while she was out shopping with Wilmer in late July.

“Lindsay and Wilmer were at the trendy Kitson clothing boutique when three 12-year-old girls recognized her,” said an eyewitness.

“They were so sweet. They told her they were visiting Los Angeles and had never seen a celebrity before, and asked if she would pose for a photo with them.

“Lindsay turned her back to them, grabbed some clothes from the rack and went straight to the dressing room without acknowledging them. They were crestfallen.

“Lindsay then told one of the salesgirls, ‘I need some privacy. I need you to close the shop for me.’ So the manager asked everyone to pay for their stuff and leave, and Lindsay got the store to herself.

“It was a classic case of seeing a star at her worst.”

‘LIKE DIRT’

The former friend added: “In her speeches after winning awards, and in interviews, Lindsay always thanks her young fans, saying that without them she wouldn’t be where she is today.

“But she’s unappreciative of her young fans. She treats them like dirt.

“The bottom line is that Lindsay can be one of the cruelest, nastiest stars going.

“The girl needs a big wake-up call!” — ROBIN MIZRAHI and TIM PLANT