Checkout the book Cinderella Ate My Daughter: Dispatches from the Front Lines of the New Girlie-Girl Culture by Peggy Orenstein and the Bloomberg article “Lego Is for Girls.” Here is an excerpt from the article:
Lego confirmed that girls favor role-play, but they also love to build—just not the same way as boys. Whereas boys tend to be “linear”—building rapidly, even against the clock, to finish a kit so it looks just like what’s on the box—girls prefer “stops along the way,” and to begin storytelling and rearranging. Lego has bagged the pieces in Lego Friends boxes so that girls can begin playing various scenarios without finishing the whole model. Lego Friends also introduces six new Lego colors—including Easter-egg-like shades of azure and lavender. (Bright pink was already in the Lego palette.)
Then there are the lady figures. Twenty-nine mini-doll figures will be introduced in 2012, all 5 millimeters taller and curvier than the standard dwarf minifig. There are five main characters. Like American Girl Dolls, which are sold with their own book-length biographies, these five come with names and backstories. Their adventures have a backdrop: Heartlake City, which has a salon, a horse academy, a veterinary clinic, and a café.