Recently, fans noticed that the Star Wars Episode VII IMDb page listed Ridley as playing Jaina Solo in the new film. Jaina, of course, was the daughter of Han Solo and Princess Leia in the now non-canon Expanded Universe. She was the only one of the three Solo children to survive throughout the many EU novels, and was beloved by EU fans. As we know from Lucasfilm, however, the Expanded Universe is no longer part of official canon, so we can be pretty sure that Jaina Solo won't be making an appearance (not to say that Ridley couldn't be a newly named daughter of Han and Leia, though).
After fans noticed the listing, Ridley herself tweeted a response, saying "the world and his wife can update IMDB. Just saying." The tweet, which has apparently since-been deleted (but can be viewed on TheForce.Net), refers to the fact that IMDb is user-generated, and cast lists can be updated by anyone. So while IMDb can be a way to find correct information, you should always make sure it's independently verified.