I was talking to Tammy about the rumors re: Dani's eating problem and she tells me that Dani eats a lot when she sees her at the players' restaurants.
As a former competitive junior, I can tell you that I was pretty thin, too, but working out 4 hours a day will do that, even if you eat McDonald's, Burger King, and Taco Bell afterwards.
I think Dani just has an extremely effective metabolism. It's just the media glare and unflattering articles pre-Wimbledon that got to her, I think.
That's just my opinion...
Good luck, Dani! Ignore everybody and get back to your brand of tennis!