Demi Lovato is officially unstoppable! In her second week of Pop Clash, the singer's 'Nightingale' beat out Kelly Clarkson's 'Heartbeat Song.' This round, Demi faces off against Fifth Harmony's 'Worth It.'

Demi opens up to her fans more than ever with 'Nightingale.' She uplifts so many of her listeners that it's a huge change to hear her sing about needing a little support herself. But it's the authenticity (oh, and that incredible voice) that draw so many people to Demi. And did we mention that 'Nightingale' gives us chills every time we hear it?

Speaking of self-assured ladies with amazing vocals, Fifth Harmony's new track, 'Worth It,' is your new favorite confidence booster. There's nothing we love more than women who demand respect because, well, they're worth it. We have a feeling this sleek, pump-up track (featuring Kid Ink!) will be huge in 2015.

Who should win this week's Pop Clash? You can vote for Demi or Fifth Harmony once an hour until the polls close at 3PM ET on Jan. 26.

Watch Demi Lovato's 'Nightingale'

Listen to Fifth Harmony's 'Worth It.'