Shop Happy Girl

What the hype with Abercrombie, Hollister, Lucky Brand, etc... Are these clothes just for kids? What's the deal? Are these brands made for teens & college kids? Do they run small with their sizes? I'm in my late 20's and don't like "grown up" clothes, I think they're boring. Will I look silly wearing these brands? I like the Gap, American Eagle & Aeropostel, I think Abercrombie, Hollister, Lucky Brand, etc are all way too expensive. What are good brands/styles for women in their late 20's?? ( I don't get dressed up and NEVER wear dresses, I'm a jeans & t-shirt girl) Any ideas??? I'm not 20, I'm 28 and have a 6 month old baby if that helps. I'm a career mom but on the weekends, I ditch the office attire and want something cute to wear.