Lovato lost her father, Patrick Lovato, last month after he lost the battle to cancer, reports conatctmusic.com.
"With Demi having just lost her dad, she feels a special bond with Paris. She told Paris about how she'd endured horrible bullying about her weight and her looks and even nasty comments about her estranged father.
That struck a chord with Paris because of her own controversial father and like Demi, she's been dieting for years," a source was quoted as saying.
"There are so few people in Hollywood who show up during the tough times but Demi is the real deal," the source added.
Lovato recently partnered with a mental health charity to honour her late father to help those with mental illnesses and seeking treatment.