Viewers saw Mecklenburgh discover Falcone's betrayal on the latest episode of the ITV2 reality show and tomorrow night's edition will feature a showdown between the pair.
Sources say that the couple - who briefly separated last year over Mecklenburgh's affair with ex-boyfriend Mark Wright - have since decided to call time on their relationship.
"After all the hassle Mario gave Lucy about her fling with Mark, she was gutted to learn he's been texting and emailing girls," a friend told the Daily Star.
"Lucy was determined to make their relationship work so it's been a real kick in the teeth."
Falcone apologised for his actions on Twitter this week, writing: "Everyone makes mistakes.. I am only human. I am so sorry for hurting you @lucy_meck... I will always love you baby x (sic)."
When their TOWIE co-star Debbie Bright offered her support, he replied: "I have been a silly boy... Love her with all my heart!"
The Only Way Is Essex continues tomorrow (February 5) at 10pm on ITV2.