The reality star has been feuding with Faiers in the latest series of the ITV2 show over claims that she has proof Mario Falcone cheated on Mecklenburgh.
The pair previously tried to resolve the situation, but in tomorrow night's show, Mecklenburgh tells co-stars Lydia Bright and Danni Park-Dempsey: "If she had proof, when I went round to her house, why didn't she give me the proof then, rather than make up with me and carry on starting it all up again?
"Let's be fair - it's not the first time she has stabbed me in the back.
"I broke up with Mark Wright and then that night she got in a cab with him and slept with him. That's not a friend."
Meanwhile, Charlie King is angry when he finds out that Bobby Norris confided in his ex-girlfriend Gemma Collins about his feelings for King.
Mecklenburgh previously admitted that Faiers's claims tarnished her engagement to Falcone.
The Only Way Is Essex continues tomorrow (August 15) at 10pm on ITV2.