But their feuding came to a head this week, when Demi tweeted about singing her song "Sorry Not Sorry" directly to a bully.
"The other night I got to sing SNS directly to one of USA's most notorious bullies. It felt so f***ing great. That's what the song is all about!!! Sorry not sorry that you were in the audience watching me kill it," she wrote.
She followed it up with another tweet saying, "And btw - he's remaining nameless because he doesn't deserve the relevance that he doesn't have anymore."
Many people quickly assumed that she was talking about Perez.
Everyone knew he was there because he posted a review about her performance.
"I am a Demi Lovato fan. She wasn't bad. She was better than before. I have nothing bad to say."
After seeing her tweets however, he has made a video in response. "Demi Lovato claims to be an anti-bullying activist. But she sure is coming actress like a bully to us!"
He even went on to say her show was "cheap".
Demi has yet to respond to Perez.