Life & Style Exclusive: Lindsay Lohan Celebrates Her Sister Aliana's Birthday with Champagne and Sparklers

122211_lohan_MC248721.jpgNow that she's 18 years old, Lindsay Lohan's model sister, Ali, would like to be called by her full name, Aliana Lohan.

Multiple sources confirm to Life & Style she prefers the name Aliana, because it sounds more mature.

And with her passage into adulthood, the Lohan family (sans father Michael) feted Aliana with a birthday celebration at Beaumarchais restaurant in NYC on Dec. 21.

Lindsay, along with a group of her friends, mom, Dina, and younger brothers Cody and Michael Jr. -- who was celebrating his 24th birthday -- ordered from a prix fixe menu that included tuna tartare and truffle gnocchi.

"It's clear Lindsay and Michael Jr. are very close. They were talking a lot and Michael had his arm around her at one point. She seemed to be confiding in him," an eyewitness tells Life & Style. She also went outside to smoke cigarettes with her mom at one point.

But a celebration wouldn't be much without champagne!

Later on in the evening, the Playboy cover girl requested just that.

"Lindsay ordered a bunch of glasses of champagne for the table and switched to drinking that," the eyewitness tells Life & Style.

During the big bash, Lindsay and Aliana snapped photos together on Lindsay's camera before Lindsay got up to ask the restaurant staff to prepare a cake and champagne sparklers for the table. "The staff brought out cake and two brownie sundaes while everyone sang," the eyewitness tells Life & Style. "Lindsay toasted with champagne."

Although Aliana is super svelte, she doesn't seem to be watching what she eats. Adds the eyewitness, "She had a lot of bread, a big salad and a bunch of her brownie sundae."

Photo Credit: Startraks