The surprise denial came after fellow participant Cathy Evans confronted Hayley about flirting with her own partner, Josh Pihlak, during the recent dinner party on Wednesday night.
Hayley had put her arm on Josh's shoulder while the pair laughed and chatted with others at the table, which raised some major red flags for Cathy, who admits she has trust issues.
"I started to get threatened and jealous that he was talking to all the girls," Cathy admitted the next day while talking to Stacey and Hayley about the fight broke out between the pair shortly after the incident.
But according to Hayley, Cathy didn't have anything to worry about.
"Was I flirting with Josh? Or was Josh flirting with me? Absolutely not, that’s my husband’s best friend," Hayley said.
"Are you kidding me? I wouldn’t flirt with someone else’s husband anyway.
"I’m all about staying true to girl code. No. That’s absurd."
The bodybuilder's apparent conviction made us wonder, just what changed between this moment and the apparent hookup with Michael?
It was none other than fellow MAFS bride Vanessa Romito who spilled details of Hayley and Michael's shock affair.
"It definitely happened."
And it wasn't a one-time thing, with Vanessa saying the duo "hooked up multiple times" – and that feelings between them intensified quickly.
This isn't the first time Hayley – who has called herself "a good egg" – has spoken about respecting "girl code".
During the hen's night, in episode 1, as the girls were cheersing each other, Hayley loudly proclaimed that they should all promise not to shag each other's partners.
According to Vanessa, the alleged affair took place in her hotel room while David's wife Stacey was in Adelaide with her two young sons.
"Michael walked into our room. He was really drunk and so was Hayley," Vanessa spilled. "Hayley said, 'My husband doesn’t want to f--k me.' And I said, 'Mine doesn’t either.' [Michael] turned around and said, 'I would f--k both of you.'"