Kyla DeTienne has a good thing going at Birds & Belles. Her concept of buying and trading better used garments is a modern take on the resale model: Bring in your still-stylish, in-season, stain-free trade-ins for cash on the table, or take store credit — at a rate of 50 percent above the straight buyout price. It keeps the clothing moving in and out, making for new surprises every time you shop. DeTienne also supports local artists by carrying some new merchandise, including hand-painted bags and upcycled assemblage jewelry, further lending a funky vibe to the neighborhood boutique.