She's a terrible director. How much money her movie made, doesn't make her worthy of directing a good script. If she had directed The FIghter, it would have been critically panned. The reason Twilight is so successful, is not because it's a well directed film, but due to it's subject matter and that it's based on an already successful book series.
Also, if she was selected to direct a film that could "only be directed by" a woman, I doubt she'd be complaining of sexism. I'm sure it goes the other way on occasion.
I'm guessing the movie will be crap, if they chose Kristen for the lead role. She's the same person in every movie. I liked her in The Runaways, but that's about it. There are two Snow White movies in the making and I'm guessing The Brothers Grimm: Snow White will be the better of the two. Studios usually try to cash in on a theme by dishing out a quick, sloppy film that mimics another better film coming out at the same time. Both Kristen and Selena Gomez were considered for this role, which shows that the studio is just trying to cash in on someone popular rather than choose a good actress.