In scenes to be featured in Sunday's instalment of the ITV2 reality series, Mecklenburgh confesses that she did sleep with ex Mark Wright and has been lying about the fling for months.
"I wanted to meet you 'cos I've never been completely honest about that night. I think you know that," Mecklenburgh tells Falcone.
Falcone replies: "You lied for the last two months not just to me, to my whole family. What sort of person does that make you? How can you say anything? There is nothing more to say!"
Wright claimed on the show that he had spent the night with Mecklenburgh two months ago, shortly after he split from Lauren Goodger.
Wright's sister Jess also claimed she had proof of the affair in the form on a text message from Mecklenburgh, who asked Jess to provide her with an alibi. The couple were rumoured to have split back in October over the claims.
Meanwhile, Wright and Goodger argue in tomorrow's episode after she brands him "very disrespectful" for getting with Sam Faiers so quickly after the breakdown of their engagement.
The Only Way Is Essex continues tomorrow night (Sunday) at 10.15pm on ITV2.
> The Only Way Is Essex Lydia Bright jealous of Arg, Gemma relationship