Mariah Carey on Demi Lovato: 'I Don't Know Her'

Andy Cohen of "Watch What Happens Live" asked Carey about Lovato and Ariana Grande.
1:46 | 12/20/16

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Transcript for Mariah Carey on Demi Lovato: 'I Don't Know Her'
Finally, a lesson for young pop stars. When you sit at the feet of a giant, you're bound to catch some shade. What do you think about people referencing I don't know her all these years later? I still don't know her. Reporter: From TMZ's cameras to appearances on "Watch what happens live" with Andy Cohen -- I don't know her either. The famous phrase I don't know her taking on a life of its own. Is it possible two mega stars like Mariah and J. Lo have never met? Apparently so. Do you know J. Lo at this point? I'm forgetful. ??? Why so obsessed with me ??? Reporter: Fans obsessed with drama. Now t-shirts, hoodies, even pins with the phrase. Mimi seems to shake it off. ??? Shake shake shake ??? Reporter: Except when it comes to demi Lovato who stood up to M.C. On Instagram. She said, Mariah's a legend and she's so talented but she disses people, it's nasty the way she treats Jennifer. What would you say to demi? I don't know her either. I wouldn't say anything to her. She should come up, introduce herself to me, say, here's my opinion, what do you think about it? That's how you handle , okay? Reporter: Feuding divas are fan fodder. One of them taking to Twitter writing, all I want for Christmas is for Mariah Carey not to know me either. Another, omg, yas, Mariah CARA. J. Lo isn't the only one. She says she doesn't know Madonna. Never had a conversation. She doesn't know Miley. I think we met if a bathroom, I don't know. Reporter: She knows Beyonce. And how about Britney spears? What about Britney? I love Britney. They loves Britney. Thank you for watching ABC news.

This transcript has been automatically generated and may not be 100% accurate.

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