This week on So You Think You’re an Adult, one woman asked whether she should put a stop to her friend’s upcoming wedding after finding out she is cheating on her fiancé.

“I’ve discovered that one of my close friends has been sleeping with somebody she works with and is due to get married [to another man] this year,” she told Moncrieff.

“She is so blasé about it, but I just can’t stop thinking about what she is doing.

“She fully intends on going through with the wedding, which is going to cost an enormous amount of money.

“She told me after a good few drinks one night and said she couldn’t imagine having sex with one person for the rest of her life and she was having a lot of fun with this guy.

“I know both her and her fiancé; we all grew up together and they have been childhood sweethearts.

“I’m due to be a bridesmaid, but I feel so guilty if I say nothing.

“If I speak up, I lose her as a friend because this will blow up their lives.

“What should I do?”

Broadcaster Barbara Scully said that while she would normally advise letter writers to mind their own business, this situation called for an intervention.

“This poor man fella is going to walk blindly into a very serious commitment to this woman who isn’t serious at all, and he needs to know that,” she said.

'She's not a friend to you'

Actress Mary McEvoy said that this woman’s first port of call should be to strong-arm her friend into admitting her infidelity.

“I think she should say, ‘You can carry on if you want; I’m not cosigning your bullshit, I’m not going to be your bridesmaid’,” she said.

“You can do what you like after that, but [she should say], ‘I am not going to participate in you basically lying through your teeth to this man, and you’ll probably end up ruining his life’.

“She’s not a friend to you either, because if she’s capable of doing that to another human being, she’ll do it to you as well.”

However, both women agreed that the letter writer should not be the person to tell the groom.

Main image: Bride in wedding dress crying. Image: Wavebreak Media ltd / Alamy. 2 May 2017