Chyna, 28, was spotted cozying up to another man at the Super Bowl game on Sunday, Us Weekly reported.
According to an eyewitness, Chyna was getting close to someone other than her fiance at Estrella's MA Theater in Los Angeles when the New England Patriots played the Atlanta Falcons on February 5.
The source told Us that Chyna and the mystery man -- who was wearing a Patriots beanie -- were sitting so close together that they looked like a couple. The makeup artist was also allegedly overheard telling a friend that while she is "still with Rob," they are not currently living together.
Chyna alluded to issues in her relationship with Kardashian on Monday when she Snapchatted, "It's funny when people say they wanna be great but sleep until 3PM etc," seemingly referring to Kardashian, who has struggled to lose weight for years now despite Chyna's recent inspiration and motivation attempts.
The couple has had a tumultuous romance since getting engaged in April 2016 after only three months of dating. Kardashian seems to have moments of insecurity since he's battling depression among other issues, while Chyna -- as shown on the pair's E! reality series Rob & Chyna -- can often lose her temper.
In late December, Kardashian, 29, apologized to the mother of his child for a blowout fight, revealing that he was "embarrassed" by his actions and "seeking help to deal with his flaws." She had moved out of their shared home at the time and taken Dream, their two-month-old daughter, with her.
"I'M DONE ! This entire year I have done nothing but help Rob! It's so SAD & PATHETIC how low he's stoop to cover up HIS PERSONAL ISSUES! Rob is mentally ill & refuses to seek help! He self medicates which makes it worse," Chyna wrote in a since-deleted post on social media in the heat of the argument.
"This weekend I was in an emotional bad place and did some things that embarrassed myself and my family. I apologize... You're a great mother to our child and I love you," Kardashian eventually replied.
Chyna's representative declined comment on the source's claims Chyna was getting close to another man at the football game.
Rob & Chyna was renewed for a second season by E! a couple of months back and is expected to premiere this year.