Lauren Alaina went a little bit country, a little bit rock 'n' roll for the "American Idol" finale.

The 16-year-old Georgia peach was styled by the show's ladies' costume designer, Soyon An, to reflect the country crooner's broad crossover appeal. "I used fashion as a tool to show her diversity," An tells StyleList exclusively.

For three powerful performances the diva-in-training --who was battling strained vocal cords-- went from edgy black to an ethereal topaz minidress that had the Grand Ole Opry bedazzled all over its layers.

Here, An gives us the behind-the-seams dish on the night's style high notes:

To sing Carrie Underwood's "Flat on the Floor," Alaina took to the stage at Los Angeles' Nokia Theater in black and metallics that An chose to make her look "strong and fierce." "She [was] wearing a dress [sourced] from Kitson that has all the sparkle a girl needs, tights to make it young and a silver skin leather jacket to bring the rock and some sparkly jewelry to make it fun and not so serious."

Fashion Credits: Shoes Badgley Mischka, jewelery Bijou Tresor.

Tonight either Alaina or fellow country teen Scotty McCreery, 17, will win the "American Idol" title and An says fashion-wise, her young charge is ready for the part. "She has come so far from when we met. She is gaining self-confidence in her body and is learning what works for her body type and how to make her shape work for her. She's learned to balance between not enough and too much. She's learned about color and which ones work for her and how to accessorize. I think she's ready for stardom and ready to show the world what she's capable of."

Fashion Credits: Dress For Joseph, leggings David Lerner, shoes Old Gringo, jacket Alexis, jewelry Kitson and Bijou Tresor.

For Alaina's second song, "Idol" winner Carrie Underwood, chose the Pam Tillis ballad "Maybe it was Memphis" and the teen looked the country part in a sparkly, topaz hoedown dress that An chose to coronate the cowboy princess. "It was Memphis! I wanted her to be just that," An says, telling us the look was her favorite of the night. "It was super slimming and flattering for her shape and very Lauren."

Fashion Credits: Dress sourced from The Mint Collection in Los Angeles, boots 1883, ring and earrings Bijou Tresor and guitar necklace, the Dolly Parton collection.

For her third and most emotional performance, Alaina sang a new song, "Like My Mother Does" while serenading her mother without missing a beat. She wore a white, floor-length gown by Adrianna Pappel trimmed with a spray of garden flowers at the hemline that kept it young and fresh. "The song chose that dress. It was perfect, age appropriate and just enough for the finale and the butterfly chandelier earring and floral bracelet created a beautiful story," An says.

For more "Idol" fashion tips from An, check out her personal blog and follow her on Twitter where she often comments on the show's fashions.