But it looks like their romance could soon be over after Arg was pictured leaving a nightclub and getting into a car with two mystery women - while on a night out with best pal Mark Wright.
After spotting the pics the following morning, an enraged Gemma, 31, tweeted: "You slept with someone else last night you disgust me you cheat!!!!"
But she quickly deleted her message and Arg, 24, responded: "Accusations because of a picture of my friend n his cousins. Not even a rumour or any truth at all. Call before u take 2 Twitter, so unfair!"
A week on, things are still far from settled between them as Gemma struggles to get over the pictures - and she is blaming Mark.
"Gemma didn't want Arg going out with Mark in the first place, especially not to Faces," a source told Reveal. "She made it very clear she wasn't happy about it. She doesn't think he's a good influence on Arg.
"She might publicly claim that she doesn't want to get in the way of their friendship, but put it this way – she gave him an earful when she said he planned to go out with Mark, so needless to say she was prepared for the worst."
While Arg is insisting he's innocent, he didn't help himself when, earlier in the day, he tweeted: "@missgemcollins got nothing 2 worry about! Me n @MarkWright_drunk n going Faces. Wat could go wrong?" before adding a photo of the pair of them in Mark's convertible sports car.
But Gemma simply replied: "You know you ain't gonna get better than my candy!!!"
"She definitely gets more jealous than Arg – but then she has good reason to. He's been in the limelight longer than she has and he always has girls throwing themselves at him.
"She constantly reminds Arg how the girls who try it on with him are only after him because he's on telly, and it's not real.
"Arg is getting fed up with Gemma's constant bossiness. She's always telling him what to do, and it's obvious he's not very comfortable about it. She calls all the shots in the relationship and is constantly talking over him."
Read the full story in this week's Reveal magazine, out now.
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