The Youtuber fired back, writing on Twitter, "Wtf is this b?"
On Wednesday, Thorne, 21, revealed on Twitter that the two “are no longer good,” claiming the YouTuber, 21, “broke girl code.”
“I’m over it,” Thorne added.
Mongeau appeared to be clueless as to what exactly Thorne was referring to, as she wrote back, “?????”
“Imagine taking every time ur mad at me to Twitter but then telling ppl how much u care about me…….. wtf is this b :/,” Mongeau tweeted.
Thorne continue the argument alleging that Mongeau “started dating me for Twitter.”
“How about u answer ur phone and talk to me instead of being on Twitter,” Thorne added.
A rep for Thorne did not immediately respond to PEOPLE’s request for comment.
Thorne and Mongeau dated for a little over a year. In February, Thorne announced on Twitter that the pair had split.
“Tana and I aren’t together anymore, pls stop asking. We love U guys,” Thorne shared.
Mongeau also shared the news, writing, “i love her forever don’t get that twisted. she changed my life forever. don’t rly wanna talk on it.”
Mongeau also reassured fans at the time that there was no bad blood between the former couple.
“There’s no negativity at all,” Mongeau tweeted.
Their surprising feud comes less than a month after Thorne wished Mongeau a happy birthday with a heartfelt tribute on Instagram.
For Mongeau’s 21st on June 24, Thorne shared a photo of herself and the influencer sharing an intimate embrace while on a yacht.
“Through thick and thin 😭🤧 I love you Tana happy bday you beautiful beautiful special girl,” Thorne captioned the heartfelt post.
In response, Thorne shared a slideshow of photos that show her crying on her Finsta account, which is an alternative Instagram account that is often more honest.
“When ur ex gets engaged 😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭😭,” Thorne captioned the post.
The post caught the eye of Mongeau, who commented, “omg.”
Mongeau shared the news about her upcoming union to Paul just hours into kicking off her birthday.
Mongeau dismissed rumors that the pair, who began making videos together about their relationship last month, were playing a joke on their followers.
In response to a tweet from a fan who wrote that they would be “pissed” if their engagement turned out to be a stunt, Mongeau wrote, “it’s not. i’m engaged. holy f—.”
The couple are set to tie the knot in a televised wedding in Las Vegas at the Grafitti Mansion on July 28. MTV will film the ceremony.
According to a press release about the pair’s upcoming nuptials, the wedding will be followed by a reception at the Sugar Factory, which will feature a full red carpet.
While no guests have been confirmed, the event is promised to be “star-studded.”
Paul, 22, revealed their wedding date to a crowd at VidCon on Saturday. In a video shared by another YouTuber, Mongeau was on a panel giving a Q&A session to attendees when Paul appeared to surprise her by showing up on the stage, with Mongeau telling the crowd she was “speechless.”
Paul then read Mongeau a poem, recounting the day they first met and suggesting something intimate happened between the two, before diving into their relationship.
“Two years later we turned into ‘Jana,’ no more broads in Atlanta, no more girls caught on camera. I’m loyal to you and all the spray Tanas,” he wrote.
As Mongeau and Paul bask in pre-marital bliss, Thorne is also content with her love life.
Late last month, just a week after news of Mongeau’s engagement broke, Thorne posted a series of cuddly photos with boyfriend Benjamin Mascolo.
The images were taken while the pair, who are currently in a long-distance relationship, enjoyed the sun together on a boat during a trip to Sicily, Italy.
Sitting on the Italian singer’s lap, Thorne flashes the camera a big smile in one photo, while in another she gives her boyfriend a kiss on the lips. “I’m very happy w you,” Thorne captioned the photos, adding a blue heart emoji.