The Geordie Shore star told The Sun Online she thinks the relationship between Charlotte and Gaz is done and dusted, after their Twitter row last week and Charlotte's decision to quit the show.
"That relationship is definitely at its dead end - I just think she can do a lot better than him and I don't think she should go back there," said Marnie.
"I really don't feel like she will, too much has happened."
"Too much has gone on behind closed doors not that many people know about," she added. "Gary is just a bit of a d**k and I don't think she will ever lower herself and degrade herself to go back there."
Marnie added in her column for Star Magazine: "I think Gaz Beadle is mentally lost. He doesn't know what he's doing and has no concept of how his actions affect others. I don't think he's ever going to truly find happiness because he's incapable of loving someone."
Charlotte, 26, split from Gaz, 28, earlier this year, after filming Geordie Shore: Big Birthday Battle, which is currently airing Tuesday nights on MTV.
He went off to film Ex On The Beach in Thailand, where he's alleged to have bedded one of his castmates – although he's claimed he wasn't in a relationship with Charlotte at the time.
Charlotte later revealed she'd been hospitalised with an ectopic pregnancy while Gaz was away, and had to have a fallopian tube removed after it tore and caused internal bleeding. She then said she'd learned about Gaz's alleged infidelity while she was recovering.
After her interview was published, Gaz gave his own version of events in a Daily Star column, saying he'd been single on EOTB and he'd volunteered to come home when he learned Char was in hospital, but she'd told him to stay as he was under contract.
He also claimed: "Both my management and Charlotte's agreed we wouldn't do any interviews or talk about this horrible situation. I hadn't planned to anyway... That is why, when I woke up yesterday to see it everywhere, I was shocked."
It led to a war of words on Twitter and Charlotte quit Geordie Shore.
But she then suggested regretting that decision, when she tweeted she'd made the "worst mistake" and felt like she was losing an important part of her life. Charlotte's tweet came after the cast flew to Magaluf to start filming series 13 without her.
That prompted Gaz to tweet: "It's not too late… Get a bag packed and get your arse out here." He added a green heart emoji and a plane emoji - but later deleted the message.
Charlotte, however, didn't respond and appears to instead be getting ready for a holiday to Australia.
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