Christina Aguilera has praised Demi Lovato for "knowing how to be strong and pull through", as the singer continues to rebuild her life following a near-fatal drug overdose last year (18).

The 26-year-old checked herself into rehab following July's overdose, and took to social media earlier this month to mark six months of sobriety.

Demi posted a picture of her blue sobriety coin, given to members of Alcoholics Anonymous or other 12-step recovery groups, that she held in her hand on her Instagram Story.

Now Christina, who is up for a Grammy Award alongside Demi for Best Pop Duo/Group for their single Fall in Line, has spoken in support of her friend and collaborator.

"Demi was just such a sweetheart to work with and to shoot that video with," Christina told the Associated Press. "Just to unite with a female that also grew up in the business and knows what's that's like and to have her own stories and her own journey."

"She's such an admirable young female who is figuring her own stuff out and knowing how to be strong and pull through. Everybody has their own things they go through, and I just am so proud of her and I just think she’s so adorable and such a talent, such a fierce talent."

It's not the first time Christina has voiced her support for Demi. After the young star shared a fresh-faced selfie last month as she enjoyed a jiu jitsu session, Christina commented on the Instagram snap: "And we keep on tickin - till the end of time - I looooove youuuuu! Can’t wait to continue to heave (sic) you by (my) side now. I've missed you so very much."

Meanwhile, Christina took part in a hidden camera prank on Jimmy Kimmel Live on Wednesday night (30Jan19), taking to the microphone to sing as customers waited in line at a Randy's Donuts store in the Hollywood and Highland shopping centre. While the customers queued to pick up their sugary treats, Christina's Genie in a Bottle song played, before the singer herself jumped in with some impromptu lines about those waiting for donuts.

As the customers realised they were in a somewhat unusual situation, Christina emerged from behind a curtain to hand them their donut delight - much to the shock and awe of those waiting.