MAFS AU: Bride Sara Mesa's cheating secret revealed by friend Eden Harper

A Married at First Sight Australia bride has been forced to reveal a secret that could destroy a marriage.

In the latest episode of the reality TV show, bride Eden Harper revealed she had received a text message from one of the other brides asking her if she could borrow a top for dinner.

When Harper questioned the texter as to where they were going, they replied: "I'm seeing my ex-boyfriend."

Taken aside by her husband, Harper said she was terrified of revealing the news because "they're all going to hate me when it comes out, every single one of them".

"Someone in the experiment sent me a text asking me to borrow some clothes. Because she was seeing her ex-boyfriend for dinner." 

Harper then went on to reveal the identity of the apparently errant bride, saying: "It's Sara." 

"I was sending her photos of tops [to try on] that I had and I asked her where she was going for dinner. And when I opened the text it said: 'I'm seeing my ex-boyfriend'."

Husband Jayden Eynaud told her it was her "duty" to be honest and reveal the truth about the secret meet up to Sara's husband Tim.

"Even if nothing happened, that's a form of cheating. And meeting up with your ex partner behind your back is a form of cheating. It's hit a little bit of a soft spot for me, I know what it would be like to be in Tim's situation right now. Tim deserves to know. I don't think Tim deserves that. It definitely needs to come out," Eynaud said.

"If I was Tim, I would want to know," echoed Harper.

The confrontation between Harper and Mesa over her apparent lie is set to take place in Wednesday's episode of the show.

Full episodes of the current season of MAFS AU are streaming on ThreeNow and airing on Three at 7pm Sunday-Wednesday.