The song, which featured on Christina's most recent album, "Liberation", earned the singers a place in the Best Pop Duo/Group Performance category, marking Demi's second-ever Grammy nod, and she took to social media to share her gratitude for the recognition.
"@Xtina what a dream come true...," she wrote on her Instagram Story timeline, as she circled their entry on the Grammys shortlist.
"Thank you for this opportunity.. Can't believe I'm nominated for a Grammy with someone I grew up singing to.. My idol forever... Love you sis, thank you".
Demi, who has been easing herself back into the spotlight following an apparent drug overdose in July, also uploaded the note to her Twitter page, and captioned it, "Woke up filled with hope. Dreams come true y'all... thank you @xtina. I love you so much".
Still stunned by the honour, the 26 year old went on to reflect on how much it had meant to her just to work with Aguilera.
"I grew up in Texas, singing to @xtina everyday, DESPERATELY trying to hit her high notes," Demi tweeted. "if you would've told me I'd have a Grammy nod with her I would've laughed in your face!! This is so surreal.."
I grew up in Texas, singing to @xtina everyday, DESPERATELY trying to hit her high notes.. if you would’ve told me I’d have a Grammy nod with her I would’ve laughed in your face!! This is so surreal..— Demi Lovato (@ddlovato) 7 December 2018
Christina was quick to respond to Demi, and made it clear the admiration was mutual.
"You deserve it all and getting to work with you was its own award for me @ddlovato," she replied. "There's no one I'd rather share this with!!"
The sweet exchange took place three days after Christina expressed her love for her new friend by commenting on a fresh-faced selfie Demi had posted following a martial arts workout.
"Sweaty, messy jiu jitsu hair," she wrote beside the Instagram snap, in which she looked happy and healthy, a month after completing an extended stay in rehab.
Among the hashtags she added was, "#nevergiveup," a motto Christina connected with, commenting, "I've missed you so very much. And we keep on tickin - till the end of time- I looooove youuuu (sic)."
Christina and Demi will face stiff competition for the Best Pop Duo/Group Performance Grammy. Also nominated are: Lady GaGa and Bradley Cooper for "A Star Is Born" track "Shallow", the Backstreet Boys for "Don't Go Breaking My Heart", Tony Bennett and Diana Krall on "'S Wonderful", "Say Something" by Justin Timberlake and Chris Stapleton, Maroon 5 and Cardi B for "Girls Like You", and "The Middle" by Zedd, Maren Morris, and Grey.
The winners of the 2019 Grammy Awards will be unveiled in a Los Angeles ceremony on 8 February.