Party on!

As Charlotte Grayson on ABC's hit drama Revenge, Christa B. Allen has seen a lot of big events end in tragedy. But all was well when the star celebrated her 21st birthday with a fabulous black-and-white-themed bash on the rooftop of the Petit Ermitage hotel in West Hollywood on Nov. 10.

Dressed to impress in a black Juicy Couture dress, Alexander McQueen heels, and a custom-made wide-brimmed hat with a pink ribbon accent, the actress chatted happily with family and friends, among whom were costars Gabriel Mann and Ashley Madekwe, who gifted her pal with a cobalt-blue Chanel pocket book.

(Allen also received a Tiffany's necklace but asked that in lieu of presents, guests instead make a donation to the Mayor's Fund to Advance New York City, one of many Hurricane Sandy relief efforts.)

"I tried to invite everyone who contributed to the debauchery that led up to 21," the Revenge star joked to Us Weekly at the Juicy-sponsored event. "I think 21 will sort of be the switching on of a different adventure."

The first step in that adventure? Enjoying her first legal drink: a champagne, gin, and rose cocktail called the "Bumble Bee," which Allen co-created with the bartender for the big event. But that wasn't the night's only milestone.

"This is the only birthday party I've ever had!" the actress told Us, joking that the celebration was 21 years in the making. "I'm just not much of a party person -- I never have been. But this is the perfect way to kick [off 21]."

In a way, she added, the fete was "sort of a last shebang" before her transition into adulthood.

"I've already been to college...and now I want to start a new chapter," she explained. That means "putting on my big girl pants and making it all about [my] career and building for the rest of my life. It's a big milestone, but in a different way than I think 21 usually is. I think the years leading up to 21 were a bit more fun than 21 and beyond might be."

Which is not to say she'll be all work and no play. On the contrary -- now that she's legal to drink and gamble, she has big plans to hit the town. And not just any town: Las Vegas, a.k.a. Sin City.

"[Ashley Madekwe] had her 30th [birthday] last year, and the cast went to Vegas together, [but] I was sort of denied entry because I was the only one under age," the star told Us. "It'll be nice the next time [I'm there.] I'll go to that same night club and that same restaurant and be like, 'I'm back and I'm legal! You can Google it if you want!'"

This article originally appeared on Usmagazine.com: Revenge Star Christa B. Allen Celebrates 21st Birthday With Big Rooftop Party