I wouldn't be so down on Lego Friends. My oldest daughter is a huge fan of Lego and has different sets that are Friends and some that are Star Wars. She combines them and plays with them together. Han Solo has a dog and a cat. One of the girls flies the X-wing. It's pretty cute.
Girls love role-playing and Friends provides another outlet for them. My oldest daughter loves building and then she plays with what she created quite extensively.
I find girl/boy toy segregation sad too, but I'm a woman and when I was 4 my first post-Duplo Lego sets were the early 80s "Lego Fabuland" series: anthropomorphic animal minifigs in gingerbread-looking houses with furniture and cookers and tiles with pictures of food on.
A few years later I was asking for every Lego Space set going and building planes and spaceships. The Fabuland bricks went in the big Lego bucket and would sometimes be repurposed as space station decor. So as an introduction to Lego for younger girls I don't really see a problem with it... though I'd prefer them to be less overwhelmingly pink.
Girls love role-playing and Friends provides another outlet for them. My oldest daughter loves building and then she plays with what she created quite extensively.