Looks like Demi Lovato is taking a page out of the Lindsay Lohan files, but don't worry, the cops are not involved. The singer called into a radio show Monday morning and though she wouldn't comment on that dinner date with Wilmer Valderrama, she did come forward with an even bigger secret she's been keeping. The singer revealed she has a half-sister that she just found out about last year. Wow, talk about a bombshell! We are so shocked so we can only imagine how it felt to be the one getting the news!