The reality star told Daily Star Sunday she splashed out on fancy swimwear to show on-off lover Aaron Chalmers just what he was missing when they came face-to-face abroad.
"I thought this series was going to be really happy for me and Aaron," she admitted, before saying shed' been devastated by allegations Aaron cheated on her. (He's denied this and said while he did sleep with someone, he and Marnie weren't together at the time.)
Marnie added: "As soon as I found out he had cheated I went straight online and spent two grand on tiny bikinis to show him what he's missing."
The outspoken reality star accused Aaron of cheating in an interview with Daily Star back in May, prompting Aaron to deny her claims online.
But Aaron then published WhatsApp messages he claimed were between him and Marnie, including one that said they weren't together.
"I wasn't going to do this, but I'm not being branded a CHEAT!" he told fans. "This message not even two weeks ago clearly states we are NOT together twice!! I would never hurt or cheat on Marnie if we were together, but what am I supposed to do when she is telling me we are not together.
"And ok I sh*gged someone, but ask Marnie who was the last person she had sex with because it WASN'T ME, but I'm not calling her a cheat because we were both SINGLE. Yes I am a C*** at times, but I'm NOT a CHEAT."
Aaron and Marnie finally slept together for the first time during Big Birthday Battle, after Marnie returned to the house in series 12 after previously quitting Geordie Shore following her engagemnt to Ricky Rayment. With that relationship now over, she rejoined the show.
Everything had seemed great between Marnie and Aaron during Big Birthday Battle, but it seems off-screen things were a bit rocky, as no doubt we'll find out during the next season.
Series 13 is currently filming in Kavos.