The other woman even shows up at the house -- and that's when it gets heated.
Were they or were they not on a break?
No, this isn't "Friends," but in TooFab's exclusive preview clip from Tuesday night's episode of "Ex on the Beach,", former "Big Brother" star Elena Davies confronts her ex and fellow "BB" alum Mark Jansen over whether or not he cheated on her when they were together.
After Elena walks up to Mark's face and loudly goes off on him, the rest of the house asks what went down to cause Elena to be so "pissed." According to Elena, she and Mark were given quite the surprise in the Shack of Secrets when the girl Mark hooked up with suddenly appeared and revealed details about their relationship.
"We play a video of the girl that he had hooked up with from the dating app telling me about their relationship, their situation," Elena recalls. "And bitch turns the corner and having no bra...he's like combating the truth!" she yells, addressing her ex.
"She was f--king right there!" Mark fires back. "What did I lie about?"
As Elena continues to recall things she learned from the woman who slept with Mark, Kenya Scott interrupts her and asks if Mark and Elena were still together when Mark hooked up with the girl from Tinder.
"Yeah," Elena simply replies, before Mark hits back. "Don't f--king do that," she shouts. "I broke up with you that weekend. I hooked up with her the week of Valentine's Day! I was single!"
It seems that the exes didn't yet come to an understanding after hashing out their relationship status in the show's premiere last week. Mark still claims the couple split the week before Valentine's Day and he hooked up with someone he met on Tinder shortly after. However, Elena stands by her version of the story, there was "no break" ... but she still wanted him back.
Here's how Aubrey O'Day -- who definitely seems a little interested in Mark -- reads the entire situation.
"I don't think Elena understands that -- news flash -- if one person in the relationship thinks that it's over, it's over," she says in a confessional. "She's either gonna recognize that Mark doesn't want her anymore or she's going to continue to spiral."
Check out the full clip, above. "Ex on the Beach" airs Tuesday nights on MTV.