While the first week of September used to give us back-to-school jitters (new teachers, pop quizzes and term papers-oh my!) we can proudly say that we have outgrown this trepidation. Instead, this time of the year is now filled with unbridled anticipation for the kick off of the international fashion weeks and wearing our best fall pieces. Of course, until the festivities begin and the weather allows us to try out our new slouchy coats and thigh-high boots, we have kept ourselves busy tracking down every publicist and studying our collection of look books to answer your most asked-after outfit queries for today's instalment of What Was She Wearing: Answers! Though we no longer get report cards, we do think we have gathered a truly A + quartet of girls whose outfits are as instructive as they are inspiring!

Lily Collins
Up-and-coming actress and Nickelodeon host Lily Collins looked age-appropriate and polished at InStyle's 8th annual Summer Soiree at the London Hotel in West Hollywood late last week. While the brunette beauty wore BCBG's Crepe Bubble Skirt (unfortunately, no longer available) and Theory's Rory Tailor Jacket ($375), we like Forever 21's Coronado Bubble Skirt ($15) for an electric blue substitute and Topshop's Premium Boyfriend Blazer ($125), which has a striped lining like Collins' selection. Though she opted for alice + olivia's White Chain Necklace Top ($230), we think Urban Outfitters' Fringed Rope Chain Necklace ($34) layered over your favourite white tank would be a smart and simple D-I-Y alternative. Just remember to wear a pair of complimentary and brightly hued heels to finish off the ensemble. Collins' slipped into Aldo's Kilbury Heels ($125), but you can consider Steve Madden's Merriee Peep Toe Heels ($90) as well!

Taylor Momsen
Whether dressed up as her Gossip Girl character Jenny Humphrey or just playing the part of a fashion plate, Taylor Momsen always grabs our readers' attention with her singular style! Spotted filming in Brooklyn's Botanical Gardens, Momsen wowed in a stunning plum Draped Front Mini Dress from Elie Saab's S/S 09 collection-try See by Chloe's Bow Drop Waist Dress ($395) for another lovely and feminine frock! Though she was wearing a highly covetable pair of Elizabeth and James' Elastic Wedge Sandals ($325), we also uncovered Topshop's Wren Multi Strap Wedges ($135) for a look-a-like version. Finally, don't forget to shield your eyes with a classic pair of Ray-Ban Aviator Sunglasses ($129) and layer a few delicate necklaces from Momsen-favourite Alex Woo for a little girly flair.

Though Rihanna has been known to wear some killer khaki pieces, for a meeting in Manhattan this week, she opted for a nude coloured tapered slacks. Her Chloé by Hannah MacGibbon Crepe de Chine Silk Cropped Pants ($1095, 323.602.0000) look sharp with a smart sleeveless duster cropped coat. Though she's got a lot going on here-including her exotic Pigalle 100 Pumps ($755) from Christian Louboutin-she is able to ground her fashion-forward silhouettes by wearing them in neutral hues. Try Topshop's Ruched Hem Pants ($70) with Re Collection's Cropped Waistcoat ($174) and Rampage's Victory Leopard Heels ($50) for a remarkable rendition of the songstress' assemblage. Finally, while Rihanna completed her look with a Chanel clutch and some strong golden bangles, we like Nasty Gal's Spiked Icicle Bracelet ($24) for a more budget-friendly take on her metallic accoutrement!

Olivia Thirlby
Independent spirit Olivia Thirlby looked casually chic at a Cinema Society & Hugo Boss hosted screening of Inglorious Basterds in New York this month. The actress paired a vintage embroidered blouse with a pair of cropped jeans from one of our favourite organic brands, Undun Denim. Though her exact pair is no longer available, try Current/Elliott's Boyfriend Jeans ($228) with an airy ecru blouse like Forever 21's Lace Peasant Tunic ($28) to achieve a similar ensemble. While Thirlby's hair and make-up are unfussy and beautifully undone, we think her sleek black accessories add just the right amount of urban sophistication. Glam Noir's The Stud Clutch ($62) is the perfect piece to carry your nighttime essentials, while Christian Louboutin's Peep-Toe Pumps ($625) are a versatile style that will allow you to show off a bright pedicure. The Merryann Pumps ($80) from Enzo Angiolini will do the trick as well!)-KM

Photo of Lily Collins, from Getty; Photo of Rihanna, from INF; Photo of Taylor Momsen, from Splash.