The 23-year-old singer began following Harris on Twitter on Thursday, a day after the DJ/producer slammed Taylor Swift in a multi-tweet rant.
"Demi Lovato started following Calvin Harris on twitter!" a fan site noted, pointing out that she also started following Hamilton creator Lin-Manuel Miranda and 5 Seconds of Summer drummer Ashton Irwin.
This isn't the first time Lovato has shown that it might not be all good between her and 26-year-old Swift. The "Cool for the Summer" singer openly dissed Swift in February, after the "Shake It Off" singer donated $250,000 to Kesha amid her legal battle with Sony and music producer Dr. Luke.
"Take something to Capitol Hill or actually speak out about something and then I'll be impressed," Lovato tweeted.
"At least I'm talking about it. Not everyone has 250k to just give to people," she also defended herself in a comment shared on the Instagram fan page, Proud of Swift. "Would love to but I didn't grow up with money and def haven't made as much as her. At least I speak up about sh** that's uncomfortable to talk about rather than trying to be politically correct 24/7."
She later took more shots at Swift in a May interview with Refinery29.
"There are women that I don't get along with, and that's fine," Lovato said when asked about the Twitter jab, though she did admit to getting "too passionate." "My thing is, don’t brand yourself a feminist if you don’t do the work. I have an immense amount of respect for women like Lena Dunham...or Beyonce, who make amazing political statements through their work.”
Lovato and Swift used to be notably friendly, most recently taking selfies at the 2014 MTV Video Music Awards.
Their friendship dates back to their teen years, as evidenced by this photo of the two happily posing on the red carpet at the 2008 American Music Awards.
Another source of potential drama is Selena Gomez. Lovato used to be besties with the "Hands to Myself" singer -- her fellow former Disney star and Barney & Friends co-star -- but Gomez is now obviously much closer to Swift.
Lovato seemingly threw shade at the Swift and Gomez friendship in January 2010, when a fan asked her, "How's Selena?," to which she replied, "Ask Taylor!"
"I think it's just one of those things where people change and people grow apart," Lovato said during an August 2014 appearance on Bravo's Watch What Happens Live! about Gomez, after she unfollowed her on both Twitter and Instagram.
Still, when ET caught up with Gomez at New York Fashion Week last September, she made it clear the two were past any drama.
"We went to a dinner, I think it was two weeks ago," Gomez said of reconnecting with Lovato. "We were at the dinner, we were talking about her record, my record, just kind of catching up."
"I love her. She's like family at this point," she continued. "It's just nice to be able to see people that you grew up with succeed."