What happened to Sophie Kinsella?!?!?

Why did just suddenly become Madeleine Wickham out of the blue, completely unannounced?!? Apparently she even has a few books out by that name already?? This is very interesting news to me because she is my absolute favorite author and I've read every book she's written...APPARENTLY UNTIL NOW! I'm freaking out here! But the even stranger thing is that she's still writing books under Sophie Kinsella too! Twenties Girl is coming out later this month with her "old" name. What in the h**l happened?