Waifish off-kilter girls such as Sofia Coppola and Kirsten Dunst have long enjoyed dressing down glam looks with sweet, practical flats. But these days, everyone from statuesque Hollywood A-listers to pop-star sensations have been following suit, trading in sky-high heels for comfortable footwear at even the most ritzy occasions. Leggy beauties Uma Thurman and Charlize Theron went the goddess route, pairing strappy sandals with metallic evening frocks at a charity event and premiere, respectively. Actresses Jennifer Connelly and Ali Larter paid homage to Indian summer temps by mixing light, breezy dresses with equally beach-worthy cobblery. Before a recent “David Letterman” taping, Rihanna grounded her gam-baring hemline with simple leather flats. But Keira Knightley seemed torn at the Venice Film Festival: Beneath her long-flowing gown she wore school-girlish T-strap shoes with a slight wedge heel. Guess some girls like to have their cake and eat it, too.