The current rumour is that she is dating Niall Horan of One Direction. However, he has, if not exactly denied this, at least not confirmed it, saying that he really likes Demi and she is a great friend. So they may well be dating, but it looks as if they don't want the rest of the world to know about it if they are.
Demi did say she had a crush on Neil, but then that's not the sort of thing you say about someone you are dating. Anyway, if they are together we will soon know.
In September Demi Lovato was seen out with her ex -boyfriend, Wilmer Valderrrama, at a restaurant. However, they don't seem to have spent much time together since then, while she has been spending more time with Niall Horan.
Her most recent live appearance was singing the American national anthem at a baseball match last week. On TV she is now best known as an American X Factor judge.