Hyatt, 24, says Calderwood doesn't like her and that the Scottish Muay Thai ace's boyfriend has been smack-talking her on an MMA forum in the U.K.
"@EricHolden @badmofo_jojo @Nutella_Italia Because JoJo no likey me," Hyatt tweeted in response to one of Calderwood's Twitter posts.
The feud between Hyatt and Calderwood dates all the way back to Invicta FC 4, where the ladies were originally slated to settle the score.
Hyatt and Calderwood were originally scheduled to fight each other at the Jan. 5 event, but an opportunity opened for the Aussie to move up on the card to battle Carla Esparza for Invicta FC's strawweight belt.
With Hyatt stepping up to fight Esparza on short notice, some fight fans started saying "Rowdy" was ducking Calderwood.
Hyatt fired back by saying "Dr. Kneevil" was offered the Esparza fight before her, and that the Scottish Muay Thai ace turned it down.
Hyatt revealing that info made her look fearless and also made Calderwood appear to be scared to take the title shot, thus the dislike between the two.
"She also said it was going to be an 'easy night' for Carla Esparza," Hyatt explained as to why she'd feuding with Calderwood. "She also thinks she is superior to me and her fiance mouths off on some U.K. forum calling me a dog. Such a nice boy that James Doolan.
"They must feel the need to put me down for some reason. James didn't do it directly to me like Jasminka's did, he posted on some forum my coach lurks on and he discovered it. I'll ask him for the link and post it up."
They might not have to fight each other, but their rivalry will undoubtedly make for a juicy storyline to watch during the season even if they don't end up duking it out inside the cage.
Calderwood hasn't yet responded to Hyatt's comments on Mixedmartialarts.com. She says she's just happy to be in the UFC and that she'll be working hard to stay there.
"Now that I'm in the UFC, the hard work will be trying to stay there," Calderwood said. "A lot of people get one chance and don't go back. I need to make sure I arrive there as the best possible fighter I can be."