The pop star, 26, considers herself a 'fangirl' of Aguilera, 38, and shared an Instagram story where she openly wept during one of the hitmaker's songs at the opening night of her residency at Planet Hollywood.
'The f**king queen herself. A PERFECT, perfect show.. couldn’t believe it was opening night because it was so smooth, flawless and sounded incredible,' captioned the former Disney star.
Pop icon love: Demi Lovato was overcome with emotion at Christina Aquilera's concert in Las Vegas on Friday night
The video showed the Skyscraper songstress singing to Aquilera's hits in a car with a group of friends on the way to the concert.
At the venue, Lovato and friends are blown away by Aguilera's performance.
And at one point, Aquilera - rocking a white jacket and matching thigh high boots - brought Lovato to tears with her outstanding vocals.
The queen: 'The f**king queen herself. A PERFECT, perfect show.. couldn’t believe it was opening night because it was so smooth, flawless and sounded incredible,' captioned the former Disney star
'I was entertained the entire time and was so bummed when it was over until I was reunited with this beauty,' she added to the caption on Instagram.
'I’m so so happy I got to hug you @xtina, haven’t seen you in concert since I was 14 and I can’t believe how much life has changed since then. Honored to call you a friend. keep it up queen.'
And Aquilera has as much admiration for Lovato.
Emotional: And at one point, Aquilera - rocking a white jacket and matching thigh high boots - brought Lovato to tears with her outstanding vocals
Back in December, the Dirty singer said she missed Lovato 'so much' on an Instagram.
Aguilera added: 'And we keep on tickin – till the end of time- I looooove youuuu.”
The two even performed a duet at the 2018 Billboard Music Awards.
